Abstract:
A system and method for tracking supplies, particularly medical supplies, and specifically individual medical items, to the end of the product lifecycle to the point of utilizes. RFID tag technology is utilized. This has the advantage of enabling a system that requires less or no active intervention by the medical services delivery staff, such as nurses and doctors. Nonetheless, the system is applicable to other stand-off identification systems including taggant-based systems. The system provides for the monitoring of items, such as medical items, between the distribution center, facility stock rooms and inventory cabinets, and the procedure rooms in which the items are put into use. In one example, system and method associate stand-off, such as RFID, readers with waste-disposal or refuse containers and/or readers located near the point of usage, such as in or associated with the procedure rooms in order to monitor the endpoint of the product lifecycle. Thus, the knowledge of medical item disposal or disposal of the medical item&#39;s packaging is combined with one or more prior detections of the medical item, e.g., at acquisition and when moved to a different location such as storage, to generate a usage history for the item. In all or more cases, this knowledge is acquired with out human intervention by judicious location of readers at the distribution center and/or medical facility.

Description:
RELATED APPLICATIONS 
     This application is a Continuation of U.S. application Ser. No. 11/383,422, filed on May 15, 2006, which claims the benefit under 35 USC 119(e) of U.S. Provisional application No. 60/680,732, filed May 13, 2005, both of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Radio Frequency Identification (RFID) systems have been proposed for the tracking of medical supplies in hospitals. Such systems typically involve one or more readers and many tags, each of which is attached to an item being monitored. In the case of medicaments, single-use medical devices, and implantable medical devices, RFID tags are typically affixed to or made part of the medicament container, e.g. medicine bottle, or medical device container, e.g., disposable packaging for the stent or orthopedic implant. 
     RFID tags take the form of integrated circuits, with associated antennas, that encode a unique serial number. The reader is generally in a fixed location, and items with RFID tags are detected when they enter or leave the electromagnetic field of the reader. For example, RFID readers are often placed at multiple distributed locations associated with an item&#39;s supply chain in order to monitor the item as it passes through manufacturing, transportation, and distribution. Each reader captures the RFID tag serial numbers of each item as it enters the reader&#39;s interrogation field, and data collected from all readers facilitate item tracking over time, through the chain. 
     Tracking using these systems generally deteriorates as the items being tracked approach the time and place of use, e.g., consumption, implantation, exhaustion, or disposal. It is therefore difficult to trace a particular item&#39;s full history. 
     For example, the most common practice in accounting for product use and disposition is based on manual data entry, sometimes assisted by bar-code scans. These manual procedures record the usage and disposition of supplies. Moreover, data entry often must be performed under time constraints that do not allow verification of the data entered. Consequently, error rates can be high and data quality is often poor. Indeed, the personnel performing these procedures often do not recognize them as high-priority tasks. 
     SUMMARY OF THE INVENTION 
     The present invention concerns a system and method for tracking supplies, particularly medical supplies, and specifically individual medical items, to the end of the product lifecycle to the point of use. In the preferred embodiment, RFID tag technology is utilized, since it has the advantage of enabling a system that requires less or no active intervention by medical services delivery staff, such as nurses, medical administration personnel, or doctors. Nonetheless, the system is applicable to other stand-off identification systems including taggant-based systems, such as Raman taggants systems. The system provides for the monitoring of items, such as medical items, between the distribution center, facility stock rooms and inventory cabinets, and the procedure rooms where the items are put into use. 
     In one example, system and method associate stand-off, such as RFID, readers with waste-disposal or refuse containers and/or readers located near the point of usage, such as in or associated with the procedure rooms in order to monitor the endpoint of the product lifecycle. Thus, the knowledge of medical item disposal or disposal of the medical item&#39;s packaging is combined with one or more prior detections of the medical item, e.g., at acquisition or when moved to a different location such as storage, to generate a usage history for the item. In all or more cases, this knowledge is acquired without human intervention by judicious location of readers at the distribution center and/or medical facility. 
     The system and method further utilize an inventory management system for receiving, from the RFID readers, for example, sensed tag information associated with the items. A database associates the items with the tag information and with the stand-off readers with their physical locations, and the items with a location and time when sensed by a reader. An inference module generates usage histories for the items based on data collected in the database. 
     In medical and other applications, the readers are configured to detect the presence of tags entering or residing in waste-disposal receptacles. This feature allows data to be developed about the status, location, time, and other characteristics marking the end of the item&#39;s useful life or its consumption, e.g., in the course of a medical procedure. These characteristics include the procedure associated with the final use of the product, corresponding billing data, inventory-control data, personnel involved in the procedure, and other tagged items used in the procedure. Reading the product tag at the time of disposal provides accurate confirmation that the product was in fact used at the date, time, and location at which the RFID tag was detected in the refuse container and recorded. RFID tags and readers therefore can be used to determine the final disposition of an item without the need for manual (and potentially unreliable) data entry activity by the personnel associated with the procedure. 
     In general according to one aspect, the invention features a medical item tracking system for medical items at a medical facility. The items have associated radio frequency identification (RFID) tags. The system comprises a medical supply location having a supply location reader for reading RFID tags of the medical items stored in the supply location and a procedure room RFID reader in or near a procedure room in which the medical items are used on patients of the medical facility. The procedure room RFID reader reads the RFID tags of medical items removed from the medical supply location for use in the procedure room. 
     In the preferred embodiment, the RFID tags are affixed to packaging for the medical items or incorporated into packaging for the medical items. The supply location reader automatically reads the RFID tags contained in the supply location. The procedure room RFID reader in one example is associated with a refuse container associated with the procedure room. 
     A management system is used to receive RFID tag information from the supply location reader and the procedure room RFID reader and track movement of medical items between the medical supply location and the procedure room. This management system classifies medical items as used at the medical facility if the RFID tags of the medical items are read in the medical supply location and then read by the procedure room RFID reader. 
     In general according to another aspect, the invention features a medical item tracking system for a distribution center. The medical items have associated radio frequency identification (RFID) tags. The system comprising supply location having a RFID supply location reader for reading RFID tags of the medical items stored in the supply location; and a refuse reader in the distribution center for reading the RFID tags of medical items placed in a refuse container. 
     In general according to another aspect, the invention features a medical item tracking method for medical items at a medical facility having associated radio frequency identification (RFID) tags. The method comprises reading RFID tags of medical items stored in a supply location, indicating medical items as being in an inventory when the RFID tags of the medical items are read at the supply location, reading RFID tags in or near a procedure room, and indicating medical items as being used when the RFID tags of the medical items are read in or near the procedure room. 
     In general, according to still another aspect, the invention features a method for tracking medical items in a supply chain at a distribution center. This method comprises detecting medical items in storage locations at the distribution center and reporting removal of the medical items from the storage when the medical items are no longer detected in the storage locations. An inventory database system changes the status of the medical items to removed from the storage locations in response to receiving a removal report. 
     In a preferred embodiment, the step of detecting the medical items in the storage locations comprises incorporating standoff readers in the storage cabinets. One example of a standoff reader is a radio frequency identification (RFID) reader. Standoff tags are associated with the medical items. The presence of the medical items is then detected by determining whether the standoff tags are within a detection field of the storage cabinets. The step of reporting removal of the medical items from the storage locations is performed if the standoff tags of the medical items are removed from the detection field. 
     In a preferred embodiment, the disposal of the medical items is also detected. A disposal report of the medical items is then provided to the inventory data base system, which changes the status of the medical items to indicate this disposal. In one example, the step of detecting disposal of medical items comprises associating RFID readers with a refuse container at the distribution center and then detecting the presence of the medical items within a detection field of the readers as an indication of the disposal. 
     Also, the status of the medical items relative to the distribution center is modified if the presence of the medical items is detected at a hospital. Specifically, the presence of the medical items is reported to the inventory database system, which changes the status of the medical items to indicate this presence. 
     In a preferred embodiment, the step of detecting the presence of the medical items at the hospital comprises incorporating RFID readers in storage cabinets at the hospital and associating RFID tags with medical items and then detecting the presence of the medical items within the detection field of the storage cabinets. 
     In general, according to another aspect, the invention features a method for tracking medical items in a hospital. This method comprises detecting medical items in storage locations at the hospital and reporting removal of medical items from the storage locations when the medical items are no longer detected in the storage locations. An inventory database system then changes the status of the medical items to indicate removal in response to receiving this removal report. 
     In a preferred embodiment, usage at that hospital is also detected such a by associating RFID readers, or other standoff readers, with refuse containers or procedure rooms where the medical items are used in the course of medical treatment. 
     The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings: 
         FIG. 1  is a schematic diagram illustrating a medical item tracking system according to an embodiment of the present invention; 
         FIG. 2  is a schematic perspective view of an RFID cabinet used in the inventive system; 
         FIG. 3  is a schematic plan view of a medical item with RFID tracking; 
         FIG. 4  is a schematic diagram illustrating a network for the medical item tracking system according to an embodiment of the present invention; 
         FIGS. 5A and 5B  are schematic perspective views of two embodiments of an RFID refuse container system according to the present invention; 
         FIG. 6  is a schematic perspective views of an RFID refuse container system associated with a RFID cabinet according to the present invention; 
         FIG. 7 through 9  are state diagrams showing a finite state machine that is used to determine the status of medical item usage in the supply chain; and 
         FIGS. 10 and 11  illustrate the user interface of the inventory tracking system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hospital Tracking System 
       FIG. 1  shows one embodiment of a tracking system which has been constructed according to the principals of the present invention. 
     The tracking system is described in the context of a hospital or other medical care delivery facility such as a long-term care facility, doctors&#39; office, animal hospital, and other institution that delivers medical care including state institutions and prisons. 
     The hospital or other medical care facility generally comprises a medical supply room  110  that is devoted to housing supplies including medical items, a procedure room  120  where the medical items are used, such as consumed or implanted in patients, and a local or off-site server or network area  130  that houses the information technology infrastructure for the facility. 
     In more detail, the medical supply room  110  in the example comprises a number of medical supply cabinets or other storage units  150 . In the preferred embodiment, each of the medical supply cabinets  150  is a radio frequency identification (RFID) cabinet that includes an associated RFID reader  154 . These medical supply room/cabinet readers  154  are capable of detecting and reading RFID tags of medical items stored in the cabinets  150 . 
       FIG. 2  shows one example of an RFID cabinet  150 . The RFID readers  154  for the medical cabinets  150  comprise antennas  190  that are moved in the cabinets to enable the RFID readers to scan for RFID tags in the storage cabinets  150 . This antenna scanning facilitates detection of the tags regardless of orientation within the cabinets or proximity to other RFID tags. 
     Specifically, in the example, the cabinet  150  comprises medical items  220  stored in item packages  210 . In a specific example, they are stored on various shelves. The cabinet  150  interrogates the various RFID tags of the items  210  using one or more cabinet antennas  190 . Here, antenna  190  of the cabinet reader system  154  is scanned along the length of the cabinet on an antenna conveyor  192 . The RFID controller  194  for the cabinet  150  uses the information from the antenna to read the RFID tags of the items contained in the cabinet  150 . The information is transmitted via a network interface on the controller  194 . 
     Returning to  FIG. 1 , the RFID cabinet readers  154  of the medical supply location  110  are networked on to a communications network  160 . Specifically, the readers  154  communicate via the communications network, such as a local area network (LAN), to an inventory management system  170 . In this way, the inventory management system  170  is able to track the presence of the medical items in the storage cabinets  150  in real-time without intervention by staff. Thus, there is no action required by the hospital personnel in order to enable the inventory management system  172  to detect the presence of the medical items. Further, there is no staff intervention required when items are removed since the periodic scan of the cabinet contents by the readers  154  detect removal, which is then reported to the inventory management system  170 . 
     Most often the medical items  220  are removed from the medical supply location  110  when they are going to be used in the treatment of patients at the facility. Medical procedures requiring the items often are performed in procedure rooms  120 . In some examples, this room is simply a patient examining room for simple procedures such as injections. In other examples, the procedure room is an operating room a diagnostic or monitoring room, or a single use room such as a catheter lab. 
     In one example, the procedure room  120  comprises, for instance, a procedure table  180  for the patient. The medical personnel  182  will then perform the procedure on the patient. Typically, there is a sterile field  184  that is defined in which the sterile items of the operation are contained. 
     The procedure room  120  has one or more associated procedure room RFID readers. In the illustrated example, the procedure room has an RFID reader associated with a refuse container  186  system and/or an RFID reader associated with a workstation  188 . These RFID readers are used to detect the usage of the medical items in the context of the procedure taking place in the procedure room  120 . 
     In other embodiments, the procedure room RFID readers are located in an adjacent room such as a preparatory room. Alternatively, the RFID readers are located at the entrance to the procedure room so that RFID tags of items are read when they are carried into the room. 
     In one example, the medical personnel  182 , after removing the medical item from its container dispose of the container in the refuse container system  186 . In this example, the RFID reader of the refuse container  186  automatically detects the presence of the RFID tag in or on the medical item packaging. This information is sent via the communications network  160  to the inventory management system  170 . 
     In an alternative example, the RFID reader associated with the workstation  188  is used to detect the usage of the medical item. Specifically, in this example, the hospital inventory management protocol requires the hospital personnel scan the RFID tag of the medical item at the RFID reader of the workstation  188  before, during, or after the procedure. This requires more manual intervention by the personnel  182 . 
     In many aspects of the present system usage medical items is inferred from the detection of the RFID tag of the medical item by an RFID reader associated with the procedure room, such as the RFID reader integrated with the refuse container system  186  or the workstation  188 . The scan at the time and place of usage provides strong evidence of the item end of life thereby improving the quality of the information contained in the inventory system  170 . 
       FIG. 3  illustrates one way of associating the RFID tags with a medical item. Specifically, a package  210  is provided that contains the medical item  220 , typically in a sealed sterile environment. The RFID tag  230  associated with the medical item  220  is attached, fixed or made part of the outside of the packaging  210 . In this way, by tracking the RFID tag  230 , the medical item package  210 , and therefore the medical item  220  is tracked in the hospital or distribution center. In other examples, the RFID tag is incorporated into the medical item itself. 
       FIG. 4  illustrates the relationship between the communications network  160 , the inventory management system  170 , and the remotely placed RFID readers  154  of the medical supply cabinets  150  and the procedure room RFID readers associated, for instance, with the refuse container systems  186  and workstations  188 . 
     In more detail, as discussed, the medical cabinets  150  have RFID readers  154  that are networked on to the communications network  160 . Similarly, the refuse containers  186 /workstations  188  for various procedure rooms in the hospital are similarly linked via the local area network  160 . This connectivity allows these devices to transmit information concerning the scanned RFID tags of medical items, which are detected in the medical supply cabinets  150  or the refuse containers  186 , to the inventory management system  170 . 
     Depending on the implementation, the communications network  160  is either a wired network, a wireless network, or a hybrid network. For example, the RFID reader of relatively stationary objects, such as cabinets, will typically connect through wired connections. In contrast, the readers of less stationary objects, such a refuse container, will sometimes connect through wireless or powerline data connections. 
     The inventory management system comprises a database  310 . This stores the inventory information. The database is managed by a database management system (DBMS)  312  that updates the information in the database  310 . This database management system  312  uses inference logic  314  and a set of rules  316  to infer the status of medical items based on the information from the RFID readers  154  of the cabinets  150  and from the refuse containers  186 . This information is then presented to users via a user interface  318 . Also, the user interface can be used to obtain manually entered information concerning the status of medical items in the hospital. 
     Ideally, the identity or category of an item, along with its RFID identifier, are entered into database  310  when the item physically enters the facility. Each time a reader senses the item&#39;s RFID tag, the associated location, time and any status information that are unambiguously derived from the reader (e.g., if the reader is associated with a trash receptacle, sensed items are usually marked as discarded) are entered into the database record for that RFID identifier. 
     For example, an RFID trash reader, after reading a tag, transmits the serial number through the communications network  160  to the DBMS  312  of the inventory management system  170 . The DBMS associates the RFID tags, read as items or discarded packagings, with earlier readings for the same item (generally involving different readers, not necessarily associated with refuse containers, such as those in cabinet  150 .). The inventory management system determines, based on the times and locations of all RFID tag read events associated with the items, the disposition, inventory status, billing data, personnel involved in the procedure at the point where the trash was generated, and other information associated with the items. 
     The user interface  318  allows users to obtain the raw record data for a selected identifier. However, the inference module  314  is used to analyze the entries in a record according to predefined rules  316 , and, based on those rules, to infer one or more aspects pertaining to the movement and usage of the item associated with the identifier. The inferred information is entered into the database record associated with the item&#39;s RFID identifier, and viewed by users via the user interface. The rules also determine when entries are flagged and dictate appropriate actions when discrepancies or error conditions are discovered. 
       FIGS. 5A and 5B  illustrate two implementations of the refuse container system  186  with integrated RFID readers. 
     Generally, the RFID reader of the refuse container  186  is used to detect all of the tags within an electromagnetic field that encompasses the entire waste container or reads the tags as they pass into the container. The reader includes a controller that decodes the unique serial number of each sensed RFID tag. 
     Specifically,  FIG. 5A  illustrates an RFID reader with a stationary antenna. Specifically, the refuse container system  186  comprises a container  410 . This is a typical, common trash container configuration that combines basically a fluid tight body having an opening  412  into which the refuse is inserted into the container  410 . 
     In this embodiment, an RFID reader antenna  414  is located near the opening  412 . In one example, it is located at the level of the opening. In other examples, it is located above the opening  412 . As a result, medical item packages  210  pass through the opening  412  and the electromagnetic read field created by the RFID reader antenna  414 . This allows the detection of the RFID tags  220 . 
     An RFID reader controller  416  drives the antenna  414  via a RF umbilical  417  and interprets the information from the antenna to determine the serial number and associated data encoded in the RFID tag. This tag information is transmitted out onto the communications network  160  via a network interface  418 . In a typical example, this network interface is an Ethernet connection or wireless link. 
       FIG. 5B  shows an alternative embodiment comprising a scanning RFID antenna  414 . In this example, the RFID antenna  414  is transported by an antenna conveyor  420 . This conveyor  420  moves the RFID antenna  414  vertically, over the length of the refuse container  410 , allowing the RFID antenna  414  to detect the RFID tags of medical item packages contained within the container  410  of the refuse container system  486 . In one example, the conveyor  420  is a stepper motor/lead screw system, enabling the antenna to sweep the container  410  from its top to bottom. 
     The antenna  414  is connected by a flexible RF (radio frequency) umbilical cable to the RFID reader controller  416  in the base of the unit. The RFID reader controller is usually implemented as a single board computer controller. The single board computer has an operating system and software that controls the conveyor  420 , obtains the tags read from the RFID tags, eliminates duplicate reads and sends the tag information, along with a time/date stamp of the read time, to the inventory management system  170 . In this way, the contents of refuse container system  186  are actively interrogated, and the RFID tags are detected and read despite their position and location. 
     In other examples, fixed loop antennas at the top, middle and/or bottom of the trash receptacle, encircling or nearly encircling the receptacle, are used. As the trash container fills, the ability of the bottom and then the middle antennas to read product tags declines, but they are still within the read range of all or most item tags in the receptacle. If the item tag is in an orientation that can be read by a fixed antenna, the bottom and middle antennas will read it with high likelihood when it is in motion, and with good likelihood when it is stationary. As additional trash is placed in the receptacle, existing trash is often displaced, providing an additional opportunity for its tags to be read by the fixed antennas. 
     A rotating field for either or both of the previous approaches will also increase the probability of read accuracy for random orientation tags as they enter the trash reader. 
     The antenna and associated design elements of the receptacle address difficulties of the environment as follows: 
     1. Difficult tag orientations. The moving antenna or rotating fields will see each tag in the trash in many orientations in three dimensions, and will be able to read virtually all tags. The fixed antennas will see most tags during most reads. The top antenna will read most tags upon entrance to the trash, since the tags will be moving at an appropriate velocity to be read. As the trash resides in the receptacle, it will often be moved when additional trash is placed in the receptacle. Both the motion and the change in orientation will allow almost all tags in the trash to be read by the stationary antennas. 
     2. Tags separated from packaging. This poses no problems. The tags can be read even if separated from packaging. The database management system contains data to associate every tag with the product item to which it was attached. The tags must maintain physical integrity, which is assured in almost all cases. In some example, two tags are placed on each product, so that if one tag is damaged or in a position that cannot be read, the trash reader will still read the other. This is a major advantage over bar codes, which can be easily damaged in a trash receptacle to the point of unreadability. 
     3. If tags are closely adjacent to each other, they are difficult to read. As trash shifts, the moving antennas will be able to read tags that may not have been read earlier, after even small displacements. Fixed antennas will pick up tags as they are thrown in the trash and will also read them as the trash receptacle is removed from the housing containing the antennas, providing a second opportunity to read the tags in the trash. 
     4. RFID tags generally withstand wetness and other conditions that affect the ability to read bar codes. The RFID trash reader are able to read all or most tags in typical disposal environments in medical and distribution center settings, where large quantities of liquid will not be present in the trash. 
     The trash reader has a power supply, either battery or wired, to power the RFID reader, its associated antenna, the digital processor and local area network (LAN) connection. The trash reader desirably withstands liquids, corrosives, medical wastes and other conditions typical of trash disposal. It is preferably washable, capable of withstanding sterilization through chemical methods, durable enough to withstand typical usage of trash receptacles, portable, relatively lightweight, and of appropriate size for the process and location. 
     Distribution Center Tracking System 
     The previous discussion has focused on techniques and devices appropriate for stand-off tracking of items, such as medical items, at the point of use, such as a medical facility. In many cases, tracking is initiated, especially for high value items such as those associated with medical applications, at the point of manufacture, followed through to a distribution center and then to the facility. Principles of the present invention can be extended to these other locations. 
       FIG. 6  illustrates another example of an RFID refuse container system. This embodiment is relevant both in the hospital context but also in the context of a distribution center or manufacturing location. 
     In this example, the refuse container system  186  is associated with the RFID supply cabinet  150 . Specifically, the cabinet  150  has shelves for holding medical items  220  stored in item packages  210 . The cabinet  150  interrogates the various RFID tags of the items  210  using cabinet antenna  190 , which is scanned along the length of the cabinet on the antenna conveyor  192 . The RFID controller for the cabinet  114  uses the information from the antenna to determine the contents of the RFID tags contained on the shelves  510  of the cabinet  150 . 
     An RFID refuse container system  186  has the container  410  and has an RFID antenna  414  located above the container mouth  412 . Thus, in this example, as the medical items are disposed of, such as after they have expired or exceeded their useful life, their disposal in the refuse container system  186  is recorded and transmitted over the communications network  160  using refuse container controller  416 . 
     In this example, the trash reader detection circuitry is external and associated with another device or object, the storage cabinet, in proximity to the trash receptacle container  410 . The antenna is located on the exterior of the cabinet (or other device) at a height and orientation consistent with placement of a waste receptacle adjacent to or below the antenna, so that the antenna—although not physically mounted on the trash receptacle—nonetheless reads all RFID tags that are placed in the container. In this example, the cabinet or other device may be marked to indicate the position at which the waste receptacle should be placed. 
     Also, in one implementation, the waste container itself has one or more RFID tags placed in or on it, thereby allowing the reader circuitry  416  to detect its presence and to identify the receptacle uniquely. In this way, a single reader is able to cover multiple trash receptacles, each identified uniquely by virtue of RFID tags associated therewith. 
     Moreover, associating an RFID reader with a storage cabinet allows withdrawal events to be recorded. When an item previously sensed is removed from the cabinet&#39;s detection field, the item&#39;s removal is reported as an event to the inventory management system. This adds to the information associated with the item and assists with inferences as to the item&#39;s state. Additional RFID readers are preferably placed in other locations, e.g., hallways and doorways. Again, the more times an item is sensed, the greater will be the detail with which its history may be traced, and the less inference that will be necessary to complete that history. 
     During setup, the RFID circuitry prompts responsible personnel to place a waste receptacle container  410  in the appropriate position if one is not present. In this system embodiment, the waste receptacle does not require its own reader, power, digital processor or LAN connection. When the external reader detects an item that is being discarded, it reports to the DBMS  312  the RFID identifier associated with the item as well as the trash receptacle(s) within its reading range. In instances where an item has two or more tags, the inventory management system associates location and time information with records corresponding to each tag ID. In particular, the DBMS (and, in some implementations, the trash reader as well) records the RFID tag serial number, data and time of the reading, and waste receptacle unique identifier, and records a disposal event. If the RFID reader is on a cabinet, a unique identifier associated with the cabinet is recorded as well. 
     A system described above provides a complete record of product usage and disposition for all products used at a facility or in a distribution center. Items not recorded by a trash reader are usually still in inventory, or must leave the facility through other controlled means such as manufacturer recalls, returns, expiration returns, defective returns, patient implants, or other related processes. The trash reader provides accountability at the end of a product life cycle in a manner similar to the way manufacturing controls document the start of a product life cycle. 
     State-Based Medical Item Tracking 
       FIGS. 7 through 9  show a finite state machine that is implemented to use the trash reader output along with data collected RFID cabinets and other sources to determine the status of medical item usage in the supply chain. 
     In the figures, D or DC is used for the manufacturer distribution center, H or Hosp for the hospital department, Cab for the RFID cabinet  150 , and Trash for the RFID trash or refuse reader  186 . Both DC and H have RFID readers for stock being shipped and received, and either or both preferably further have trash or refuse readers. 
     The figures show product states and their transitions, called dispositions. The numbers in  FIGS. 7 through 9  are keyed to the row numbers in tables 3 and 4 below that describe the state transitions. All of these states and transitions are inferred from the RFID readers at the DC and H, for both shipped/received stock and for trash readers at both locations. 
       FIG. 7  shows the basic transitions between H and DC.  FIG. 8  adds the states and transitions associated with the hospital trash reader.  FIG. 9  adds the states and transitions associated with the DC trash reader. Most of these transitions, while possible, are highly unlikely and represent errors. All are included in the finite state machine for completeness and to support error detection. 
     In one implementation, the database management system  312  of  FIG. 3  writes the current state, current disposition, next state, next disposition, first RFID read date and time, last RFID read date and time, RFID read location, type of location (hospital, DC, other supply chain point) and supporting data to the database  310  based on the inference logic  314  and rules  316 . Users access the database with preferably a Web application that supports the system via interface  318 . The application processes the data from the finite state machine and database  310  to produce measures of transactions and inventory levels at cabinets and other points with RFID readers. The trash readers at the DCs and hospitals enhance the accuracy necessary for system reports. 
     A brief summary of the finite state machines of  FIGS. 7-9  is given below. The set of states and dispositions below account for the large majority of actual transactions. Many of the dispositions and states in the figure above are error conditions and should occur rarely. In the figures: 
     1. The black dot at the top is the start. 
     2. A medical items will be first read either at DC or H, not both. 
     3. If the medical item&#39;s first read is at the DC, the normal case, it will either stay there indefinitely (until it expires in the worst case), or it will be read in the trash reader at the DC, or it will leave. 
     4. If the medical item leaves the DC, it is either read at a hospital within a given time period (typically 1-2 days) or it is lost in transit or may be at a manufacturer sales representative, who may not have an RFID reader. It may be read in the DC trash, which indicates it has been disposed. 
     5. If the medical item is first read at H, it will either stay there indefinitely (until it expires, in the worst case), or it will be read in the trash reader, or it will leave. 
     6. If the medical item leaves H, it is either read at the DC within some period (if returned) or after some period (typically two weeks) it will be assumed not to be read again. 
     7. The medical item may also be read again at H, which will occur if it was taken from a cabinet and then returned to the cabinet. 
     The possible states in the system, as shown in  FIGS. 7-9  are: 
     
       
         
               
             
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 System states 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 &lt;none&gt; 
               
               
                   
                 ReadAtDC 
               
               
                   
                 NoLongerInDCCab 
               
               
                   
                 ReadDCTrash 
               
               
                   
                 GoneFromDC 
               
               
                   
                 GoneFromDCTrash 
               
               
                   
                 ReadAtH 
               
               
                   
                 NoLongerInHCab 
               
               
                   
                 ReadHTrash 
               
               
                   
                 GoneFromH 
               
               
                   
                 GoneFromHTrash 
               
               
                   
                 AtDCFromH 
               
               
                   
                 NoInformation 
               
               
                   
                 UnableToLocate 
               
               
                   
                   
               
             
          
         
       
     
     When the system detects a state change for a medical item from RFID reads, or if a user enters a manual disposition, the DBMS  312  writes its state transition or disposition into the database  310 . The disposition (state change) occurs automatically when a box leaves a DC or H, arrives at a DC or H, is read in the trash, or is not seen for a time period. Manual dispositions (Manual) along with dispositions from information from RFID readers (RFID) and dispositions associated with timers, i.e., an item has spent too much time in a state, (Timer) are described below. 
     The list of valid disposition codes is: 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 System dispositions, or state transitions 
               
             
          
           
               
                   
                 Disposition codes: 
                 Type 
                 DispositionGroup 
               
               
                   
                   
               
               
                   
                 Defective 
                 Manual 
                 Unresolved 
               
               
                   
                 ErrorAtDCAfterGone 
                 RFID 
                 Unresolved 
               
               
                   
                 ErrorAtHospAfterGone 
                 RFID 
                 Unresolved 
               
               
                   
                 ErrorRecdAtHosp 
                 RFID 
                 Received 
               
               
                   
                 ExpiredInHosp 
                 Timer 
                 Unresolved 
               
               
                   
                 InHospital 
                 RFID 
                 Received 
               
               
                   
                 InTransitToDC 
                 Manual 
                 Returned 
               
               
                   
                 InTransitToHosp 
                 Manual 
                 InTransit 
               
               
                   
                 InTransitToRep 
                 Manual 
                 InTransit 
               
               
                   
                 InTransitToRepOrHosp 
                 RFID 
                 InTransit 
               
               
                   
                 LostInTransit 
                 Manual 
                 DC 
               
               
                   
                 LostInTransitOrAtRep 
                 Timer 
                 Unresolved 
               
               
                   
                 MfrDisposed 
                 Manual 
                 DC 
               
               
                   
                 MfrDisposedAssumed 
                 RFID 
                 DC 
               
               
                   
                 MfrDisposedRFID 
                 RFID 
                 DC 
               
               
                   
                 NewProductAtDC 
                 RFID 
                 DC 
               
               
                   
                 Patient 
                 Manual 
                 Used 
               
               
                   
                 PendingHosp 
                 Manual 
                 PendingUsed 
               
               
                   
                 PendingMfr 
                 Manual 
                 PendingUsed 
               
               
                   
                 ReceivedByRep 
                 Manual 
                 InTransit 
               
               
                   
                 ReturnToMfr 
                 RFID 
                 Returned 
               
               
                   
                 ReturnToRep 
                 Manual 
                 Returned 
               
               
                   
                 UsedAtHosp 
                 Timer 
                 Used 
               
               
                   
                 UsedAtHospRFID 
                 RFID 
                 Used 
               
               
                   
                 UsedOrMovedHosp 
                 RFID 
                 PendingUsed 
               
               
                   
                 Wasted 
                 Manual 
                 Used 
               
               
                   
                 WrittenOffHosp 
                 Manual 
                 Used 
               
               
                   
                 WrittenOffMfr 
                 Manual 
                 Returned 
               
               
                   
                   
               
             
          
         
       
     
     ‘ExpiredInHospital’ is a disposition that is automated, based on date rather than an RFID read or lack thereof. No manual input can change this disposition; the product must be removed from the shelf to change its disposition. A product can expire at any location. Expired state is a function only of the expiration time, with the following exceptions: A product cannot expire after its final disposition, either not being present in any cabinet, or after being read by a trash reader. 
     An item moves to the ‘LostInTransit’ state based on time. If it has been InTransit for, typically, three days and has not been read by a cabinet, it is moved to ‘LostInTransit’ state. A timer is also used to move products to the ‘GoneFromH’ and ‘GoneFromDC’ states. 
     The detailed finite state machine implementation that is built into the application is based on the tables below. The numbers on each row corresponds to the numbers in the state diagrams of  FIGS. 7-9 . The states are based on: 1) the latest RFID read location of product, 2) whether it is read during the latest run, and 3) its current state. 
     The application determines: 1) the next state of the product item, and 2) the next disposition of the product item. 
     The last column in the tables below indicates the type of internal database action required to implement the state and disposition: 1) UpdateEvent: updates the last event&#39;s (disposition&#39;s) date and time; 2) InsertEvent: inserts a new event (disposition) in the database; and 3) SimulateEvent: inserts a new event and then processes the inserted state to insert another event. 
     SimulateEvent is done in error cases, where a product is at a DC or H, and then appears at the other type of entity (H or DC) without having departed its last location first. This type of read causes both a departure event from the last location and an arrival event at the new location to be written. 
     Table 3 shows the latest RFID read location, current read status and current state, and then the resulting next state and next disposition (state transition) for RFID reads that occur in a hospital RFID cabinet or at the DC as product is shipped or stored. 
     Table 4 shows the same information for RFID reads that occur in a hospital trash reader or DC trash reader. 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 States and transitions based on DC and hospital cabinet RFID reads 
               
             
          
           
               
                 Cabinet/ 
                 Read 
                   
                   
                   
                   
               
               
                 Location 
                 State 
                 Current State 
                 Next State 
                 Next Disposition 
                 Action 
               
               
                   
               
             
          
           
               
                 DC 
                 Read 
                  2 
                 None 
                 ReadAtDC 
                 NewProductAtDC 
                 InsertEvent 
               
               
                   
                   
                  3 
                 ReadAtDC 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                   
                  4 
                 NoLongerInDCCab 
                 ReadAtDC 
                 NewProductAtDC 
                 InsertEvent* 
               
               
                   
                   
                  4a 
                 ReadDCTrash 
                 ReadAtDC 
                 ErrorAtDCAfterGone 
                 InsertEvent 
               
               
                   
                   
                  5 
                 GoneFromDC 
                 ReadAtDC 
                 ErrorAtDCAfterGone 
                 InsertEvent 
               
               
                   
                   
                  5a 
                 GoneFromDCTrash 
                 ReadAtDC 
                 ErrorAtDCAfterGone 
                 InsertEvent 
               
               
                   
                   
                  6 
                 ReadAtH 
                 NoLongerInHCab 
                 UsedOrMovedHosp 
                 SimulateEvent 
               
               
                   
                   
                  7 
                 NoLongerInHCab 
                 AtDCFromH 
                 ReturnToMfr 
                 InsertEvent 
               
               
                   
                   
                  7a 
                 ReadHTrash 
                 AtDCFromH 
                 ReturnToMfr 
                 InsertEvent 
               
               
                   
                   
                  8 
                 GoneFromH 
                 AtDCFromH 
                 ErrorAtDCAfterGone 
                 InsertEvent 
               
               
                   
                   
                  8a 
                 GoneFromHTrash 
                 AtDCFromH 
                 ErrorAtDCAfterGone 
                 InsertEvent 
               
               
                   
                   
                  9 
                 AtDCFromH 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                 No 
                 10 
                 None 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                 Read 
                 11 
                 ReadAtDC 
                 NoLongerInDCCab 
                 InTransitToRepOrHosp 
                 InsertEvent 
               
               
                   
                   
                 12 
                 NoLongerInDCCab 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                   
                 12a 
                 ReadDCTrash 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                   
                 13 
                 GoneFromDC 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 13a 
                 GoneFromDCTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 14 
                 ReadAtH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 15 
                 NoLongerInHCab 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 15a 
                 ReadHTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 16 
                 GoneFromH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 16a 
                 GoneFromHTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 17 
                 AtDCFromH 
                 NoLongerInDCCab 
                 MfrDisposedAssumed 
                 InsertEvent 
               
               
                 Hosp 
                 Read 
                 18 
                 None 
                 ReadAtH 
                 ErrorRecdAtHosp 
                 InsertEvent 
               
               
                   
                   
                 19 
                 ReadAtDC 
                 NoLongerInDCCab 
                 InTransitToRepOrHosp 
                 SimulateEvent 
               
               
                   
                   
                 20 
                 NoLongerInDCCab 
                 ReadAtH 
                 InHospital 
                 InsertEvent 
               
               
                   
                   
                 20a 
                 ReadDCTrash 
                 ReadAtH 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 21 
                 GoneFromDC 
                 ReadAtH 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 21a 
                 GoneFromDCTrash 
                 ReadAtH 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 22 
                 ReadAtH 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                   
                 23 
                 NoLongerInHCab 
                 ReadAtH 
                 InHospital 
                 InsertEvent* 
               
               
                   
                   
                 23a 
                 ReadHTrash 
                 ReadAtH 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 24 
                 GoneFromH 
                 ReadAtH 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 24a 
                 GoneFromHTrash 
                 ReadAtH 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 25 
                 AtDCFromH 
                 ReadAtH 
                 InHospital 
                 SimulateEvent 
               
               
                   
                 No 
                 26 
                 None 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                 Read 
                 27 
                 ReadAtDC 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 28 
                 NoLongerInDCCab 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 28a 
                 ReadDCTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 29 
                 GoneFromDC 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 29a 
                 GoneFromDCTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 30 
                 ReadAtH 
                 NoLongerInHCab 
                 UsedOrMovedHosp 
                 InsertEvent 
               
               
                   
                   
                 31 
                 NoLongerInHCab 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                   
                 31a 
                 ReadHTrash 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                   
                 32 
                 GoneFromH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 32a 
                 GoneFromHTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 33 
                 AtDCFromH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
               
               
                 *Unless, while product item is not in cabinet, a user enters a manual disposition for it. In that case, if the product item reappears on the hospital or DC shelf, its status is ErrorAtDCAAfterGone or ErrorAtHAfterGone. 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 States and transitions based on DC and hospital trash reader RFID reads 
               
             
          
           
               
                 Cabinet/ 
                 Read 
                   
                   
                   
                   
               
               
                 Location 
                 State 
                 Current State 
                 Next State 
                 Next Disposition 
                 Action 
               
               
                   
               
             
          
           
               
                 DC 
                 Read 
                 102 
                 None 
                 ReadDCTrash 
                 ErrorAtDCAfterGone 
                 InsertEvent 
               
               
                 Trash 
                   
                 103 
                 ReadAtDC 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 UpdateEvent 
               
               
                   
                   
                 104 
                 NoLongerInDCCab 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 InsertEvent 
               
               
                   
                   
                 104a 
                 ReadDCTrash 
                 NULL 
                 MfrDisposedRFID 
                 UpdateEvent 
               
               
                   
                   
                 105 
                 GoneFromDC 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 InsertEvent 
               
               
                   
                   
                 105a 
                 GoneFromDCTrash 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 InsertEvent** 
               
               
                   
                   
                 106 
                 ReadAtH 
                 NoLongerInHCab 
                 UsedOrMovedHosp 
                 SimulateEvent 
               
               
                   
                   
                 107 
                 NoLongerInHCab 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 InsertEvent 
               
               
                   
                   
                 107a 
                 ReadHTrash 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 InsertEvent 
               
               
                   
                   
                 108 
                 GoneFromH 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 InsertEvent 
               
               
                   
                   
                 108a 
                 GoneFromHTrash 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 InsertEvent 
               
               
                   
                   
                 109 
                 AtDCFromH 
                 ReadDCTrash 
                 MfrDisposedRFID 
                 UpdateEvent 
               
               
                   
                 No 
                 110 
                 None 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                 Read 
                 111 
                 ReadAtDC 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 112 
                 NoLongerInDCCab 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 112a 
                 ReadDCTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 113 
                 GoneFromDC 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 113a 
                 GoneFromDCTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 114 
                 ReadAtH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 115 
                 NoLongerInHCab 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 115a 
                 ReadHTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 116 
                 GoneFromH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 116a 
                 GoneFromHTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 117 
                 AtDCFromH 
                 NULL 
                 NULL 
                 NULL 
               
               
                 Hosp 
                 Read 
                 118 
                 None 
                 ReadHTrash 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                 Trash 
                   
                 119 
                 ReadAtDC 
                 NoLongerInDCCab 
                 InTransitToRepOrHosp 
                 SimulateEvent 
               
               
                   
                   
                 120 
                 NoLongerInDCCab 
                 ReadHTrash 
                 UsedAtHospRFID 
                 SimulateEvent 
               
               
                   
                   
                 120a 
                 ReadDCTrash 
                 ReadHTrash 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 121 
                 GoneFromDC 
                 ReadHTrash 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 121a 
                 GoneFromDCTrash 
                 ReadHTrash 
                 ErrorAtHospAfterGone 
                 InsertEvent 
               
               
                   
                   
                 122 
                 ReadAtH 
                 ReadHTrash 
                 UsedAtHospRFID 
                 InsertEvent 
               
               
                   
                   
                 123 
                 NoLongerInHCab 
                 ReadHTrash 
                 UsedAtHospRFID 
                 InsertEvent 
               
               
                   
                   
                 123a 
                 ReadHTrash 
                 NULL 
                 NULL 
                 UpdateEvent 
               
               
                   
                   
                 124 
                 GoneFromH 
                 ReadHTrash 
                 UsedAtHospRFID 
                 InsertEvent 
               
               
                   
                   
                 124a 
                 GoneFromHTrash 
                 ReadHTrash 
                 UsedAtHospRFID 
                 InsertEvent 
               
               
                   
                   
                 125 
                 AtDCFromH 
                 ReadHTrash 
                 InTransitToRepOrHosp 
                 SimulateEvent 
               
               
                   
                 No 
                 126 
                 None 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                 Read 
                 127 
                 ReadAtDC 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 128 
                 NoLongerInDCCab 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 128a 
                 ReadDCTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 129 
                 GoneFromDC 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 129a 
                 GoneFromDCTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 130 
                 ReadAtH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 131 
                 NoLongerInHCab 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 131a 
                 ReadHTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 132 
                 GoneFromH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 132a 
                 GoneFromHTrash 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
                   
                 133 
                 AtDCFromH 
                 NULL 
                 NULL 
                 NULL 
               
               
                   
               
               
                 **Items read when thrown in trash may be read again when trash is emptied. The timer filters out these reads. 
               
             
          
         
       
     
     The finite state machine also handles the ‘NoInformation’ and ‘UnableToLocate’ states and dispositions through associated logic; these are not driven by this table of logic. The ‘NoInformation’ state is used when a cabinet has been out of service for a predetermined period. The ‘UnableToLocate’ state is used when error conditions are inferred with the RFID tags on a medical item: when a tag has fallen off a product, has a duplicate serial number, or other problems. 
     The system manages the time differences in the clocks of the different cabinets, trash readers, application and database. It also handles cases where the cabinets are down and return to service with delayed reads, or network links are down between cabinets and the servers, delaying the transmission of their read data. 
     Manual State Transitions, or Dispositions 
     If the current state is ‘NoLongerAtDC’ or ‘GoneFromDC’, then Manual input can alter the default disposition from ‘InTransitToRepOrHosp’ or ‘LostInTransitOrAtRep’ to: 1) InTransitToRep: if known to be a rep PO; 2) InTransitToHosp: if known to be a hospital PO; 3) MfrDisposed: if known to be damaged or disposed at DC; 4) ReceivedByRep: if rep enters receipt in our system; 5) LostInTransit: if known to be lost from carrier report or other info; 6) PendingMfr or PendingHosp: known problem, still being investigated; 7) WrittenOffMfr or WrittenOffHosp: lost and not found, no longer being searched for; this is a terminal state for items that are never resolved. 
     If the current state is ‘NoLongerInHospCab’ or ‘GoneFromH’, Manual input can alter the default disposition from ‘UsedOrMovedHosp’ or ‘UsedAtHosp’ to: 1) Patient, if patient record number entered by hospital; 2) Defective, if ‘did not cross’ or other defect status entered by hospital; 3) Wasted, if entered by hospital; 4) ReturnToRep, if entered by rep or hospital; 5) InTransitToDC, if return entered by hospital; 6) PendingMfr or PendingHosp: known problem, still being investigated; 7) WrittenOffMfr or WrittenOffHosp: lost and not found, no longer being searched for; this is a terminal state for items that are never resolved. 
     If the current state is ‘ReadHTrash’ or ‘GoneFromHTrash’, the ‘ReadHTrash’ state, when available from RFID trash reads, supersedes the ‘NoLongerInHCab’ state and offers much greater certainty that the product was used. In practice, the hospital trash reader will result in substantially fewer unresolved dispositions, error dispositions and pending used dispositions, all of which are substantial problems operationally and occur frequently without a trash reader. 
     After a product item is read by the hospital trash reader, the following manual dispositions are allowed: 1) Patient, if patient record number entered by hospital; 2) Defective, if ‘did not cross’ or other defect status entered by hospital; 3) Wasted, if entered by hospital; 4) ReturnToRep, if entered by rep or hospital; 5) InTransitToDC, if return entered by hospital; 6) PendingMfr or PendingHosp: known problem, still being investigated; 7) WrittenOffMfr or WrittenOffHosp: lost and not found, no longer being searched for; this is a terminal state for items that are never resolved. 
     We allow these manual dispositions to be entered, even though we expect manual entry to happen much less frequently. 
     If the current state is ‘ReadDCTrash’ or ‘GoneFromDCTrash’, the ‘ReadDCTrash’ state when available from RFID trash reads, supersedes the ‘NoLongerInDCCab’ state and offers greater certainty that the product was disposed. In practice, the DC trash reader will result if substantially fewer unresolved dispositions and error dispositions, both of which are substantial problems operationally and occur frequently without a trash reader. After a product item is read by the DC trash reader, the following manual dispositions are allowed: 1) InTransitToRep: if known to be a rep PO; 2) InTransitToHosp: if known to be a hospital PO; 3) MfrDisposed: if known to be damaged or disposed at DC; 4) ReceivedByRep: if rep enters receipt in the system; 5) LostInTransit: if known to be lost from carrier report or other info; 6) PendingMfr or PendingHosp: known problem, still being investigated; 7) WrittenOffMfr or WrittenOffHosp: lost and not found, no longer being searched for; this is a terminal state for items that are never resolved 
     The dispositions would almost never be entered, as they could occur only under quite unusual error conditions. 
     If the current state is ‘NoInformation’ because a cabinet or its network connection is offline, users can input the same manual dispositions as above. If necessary to continue tracking inventory via RFID, users should put product items in other operational cabinets. Users may not enter ‘RFID’ or ‘Timer’ dispositions if the current state is ‘NoInformation’. 
       FIGS. 10 and 11  illustrate exemplary reports generated at the user interface  318  of the inventory management system  170 . 
     Specifically,  FIG. 10  illustrates an activity report. It provides information for various product groups, “blue stent,” “green stent,” . . . see  618 . This provides information concerning those items that are used, pending, wasted. Also, there is a column  620  that is associated with stents within the group that have an unresolved status. It also shows other stents that have been returned and shipped in other columns. In this way, the user interface reports to the inventory personnel for the hospital information concerning use and inventory including unresolved medical items in the inventory. 
       FIG. 11  illustrates a product search and disposition report for the user interface  318 . In this example, information associated with different “balloon-expanding stents”  624 , with different model numbers  626 , is presented, including expiration date  628  and date last read by and RFID reader is provided  630 . It also enables manual changes to the disposition in column  632 . The user is allowed to change the inventory status by modifying the pull-down menus contained in the disposition column. In this way, information for stents is manually modified to indicate other information that the inventory personnel have access to. 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.