Patent Description:
It is known that, if a coagulation time is found to have been prolonged in a blood coagulation test, a cause of the prolongation is analyzed in a cross-mixing test. In a cross-mixing test, a plurality of plasmas (mixed plasmas) are prepared by mixing a plasma from a subject (subject plasma) and a plasma from a healthy individual (normal plasma) such that the mixing ratio between the subject plasma and the normal plasma varies among the mixed plasmas, coagulation times of the plurality of respective mixed plasmas are measured, and a cause of prolonging a coagulation time is analyzed from a graph having a vertical axis indicating coagulation time and a horizontal axis indicating mixing ratio. In addition, a method in International Publication <CIT> is known as a method for quantitatively analyzing a cause of prolonging a coagulation time, on the basis of a graph obtained through a cross-mixing test. International Publication <CIT> discloses a method for analyzing a cause of prolonging a coagulation time by using a result of performing arithmetic operation with: a first quantification index obtained from coagulation times of a subject plasma, a normal plasma, and a mixed plasma that have been measured by using a blood coagulation measurement device without incubating these plasmas in advance; and a second quantification index obtained from coagulation times of the subject plasma, the normal plasma, and the mixed plasma that have been measured by using the blood coagulation measurement device after incubating these plasmas under a predetermined condition (at <NUM> for two hours).

The cross-mixing test and the method in the above International Publication <CIT> necessitates usage of mixed plasmas obtained by mixing a subject plasma and a normal plasma. However, preparation of a mixed plasma necessitates preparation of a normal plasma and mixing of the prepared normal plasma and a subject plasma, resulting in complicated work.

From "<NPL>, a characterization of the genetic background of plasma prekallikrein deficiency is known.

The present invention makes it possible to analyze a cause of prolonging a coagulation time of a blood specimen from a subject, without using a specimen obtained by mixing of the blood specimen from the subject and a normal blood specimen.

With reference to <FIG>, an analysis system <NUM> includes: an analyzer <NUM> which analyzes a cause of prolonging a coagulation time of a blood specimen (hereinafter, also referred to as "cause of coagulation time prolongation"); and a measurement device <NUM> including a detector which obtains optical information through application of light to a blood specimen in which a coagulation reaction has started. The analyzer <NUM> and the measurement device <NUM> are connected to each other with a communication cable <NUM>.

Examples of the blood specimen to be analyzed in the analysis system <NUM> include whole blood and plasma. A preferable blood specimen is plasma. Anticoagulants other than heparin, warfarin, and a direct oral anticoagulant (DOAC) may be added to the blood specimen at the time of blood collection. As such an anticoagulant, a citrate such as trisodium citrate can be used.

A subject is not particularly limited, and examples of the subject include a subject who has been found to have experienced prolongation of a coagulation time in a coagulation test. The type of the coagulation time found to have been prolonged in the coagulation test is not particularly limited, and examples of the type of the coagulation time include APTT, prothrombin time, thrombin time, and the like. Among these types of coagulation times, APTT is preferable. The cause of coagulation time prolongation is not particularly limited, and examples of the cause include the presence of lupus anticoagulant (LA), coagulation factor deficiency, mixing or administration of heparin, administration of warfarin, administration of a DOAC, and the like.

The DOAC is not particularly limited, and examples of the DOAC include factor Xa inhibitors and thrombin inhibitors. Factor Xa inhibitors are directly bound to factor Xa so as to inhibit conversion of prothrombin into thrombin. Examples of the factor Xa inhibitors include rivaroxaban, apixaban, edoxaban, betrixaban, otamixaban, razaxaban, darexaban, letaxaban, eribaxaban, antistasin, and the like. Thrombin inhibitors are directly bound to thrombin so as to inhibit fibrinogen activation that is mediated by the thrombin. Examples of the thrombin inhibitors include dabigatran, bivalirudin, hirudin, lepirudin, desirudin, argatroban, melagatran, ximelagatran, and the like.

With reference to <FIG>, the analyzer <NUM> is communicably connected to the measurement device <NUM>. Further, the analyzer <NUM> is connected to a media drive <NUM>. Further, the analyzer <NUM> is connected to an electronic medical chart system <NUM> via a network <NUM>. The network <NUM> is, for example, a local area network (LAN). The network <NUM> may be the Internet.

The analyzer <NUM> includes a controller <NUM>, an input device <NUM>, and an output device <NUM>. The controller <NUM> includes: a CPU (central processing unit) <NUM> which performs data processing; a storage <NUM> which is used as a work area for data processing; a storage <NUM> in which information to be transferred to the storage <NUM> is saved; a bus <NUM> through which data is transmitted between the devices; and an interface (I/F) <NUM> through which data is inputted from and outputted to an external device. The input device <NUM>, the output device <NUM>, the media drive <NUM>, the network <NUM>, and the measurement device <NUM> are connected to the interface <NUM>.

The storage <NUM> is composed of a DRAM and an SRAM. The storage <NUM> is a solid-state drive. The storage <NUM> may be a hard disk drive. The interface <NUM> is of Ethernet. The interface <NUM> may be of IEEE1394, USB, or the like. The input device <NUM> is composed of a keyboard and a mouse. The output device <NUM> is a liquid crystal display. The output device <NUM> may be an organic electroluminescence display. Information regarding a cause of coagulation time prolongation is outputted to the output device <NUM>. Further, a coagulation time of a blood specimen from a subject and a parameter regarding a differential of a coagulation waveform may be outputted to the output device <NUM>.

With reference to <FIG>, the storage <NUM> stores therein: an analysis program <NUM> for analyzing a cause of coagulation time prolongation; a function database DB1 storing therein mathematical expressions for use in analysis; and a threshold value database DB2 storing therein threshold values.

With reference to <FIG>, the measurement device <NUM> includes a light applicator <NUM>, a detector <NUM>, a sample preparation part <NUM>, and a controller <NUM>.

The controller <NUM> controls the light applicator <NUM>, the detector <NUM>, and the sample preparation part <NUM>, and performs data communication with the controller <NUM> of the analyzer <NUM>. The controller <NUM> includes a CPU, a DRAM, an SRAM, a solid-state drive, and Ethernet in the same manner as the controller <NUM>. The solid-state drive stores therein: a measurement program for causing the measurement device <NUM> to perform blood coagulation measurement; and waiting times described later.

With reference to <FIG>, the light applicator <NUM> includes: five light sources <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>; five optical fiber parts 330a, 330b, 330c, 330d, and 330e; and one holding member <NUM>. The optical fiber parts 330a to 330e are provided so as to correspond to the five light sources <NUM> to <NUM>, respectively. The holding member <NUM> holds the light sources <NUM> to <NUM> and light entry ends <NUM> of the optical fiber parts 330a to 330e. The light sources <NUM> to <NUM>, the optical fiber parts 330a to 330e, and the holding member <NUM> are accommodated in a housing <NUM> made of metal. Each of the light sources <NUM> to <NUM> is implemented by an LED. The first light source <NUM> generates <NUM>-nm light, the second light source <NUM> generates <NUM>-nm light, the third light source <NUM> generates <NUM>-nm light, the fourth light source <NUM> generates <NUM>-nm light, and the fifth light source <NUM> generates <NUM>-nm light. The controller <NUM> controls the light sources <NUM> to <NUM> to be turned on and off.

Each of the optical fiber parts 330a to 330e is formed as a cable obtained by bundling optical fiber element wires each having one core. The optical fiber parts 330a to 330e are bundled at intermediate portions <NUM> thereof, to obtain one optical fiber part. The one optical fiber part obtained by bundling the optical fiber parts 330a to 330e is divided into two bundles, and light outputting ends <NUM> of the respective bundles are held in outlets <NUM> provided in the housing <NUM>. Light entry ends <NUM> of optical fibers <NUM> are also held in the outlets <NUM>. Each of the optical fibers <NUM> connects the light applicator <NUM> and the detector <NUM> to each other. Light from the light applicator <NUM> is supplied via the optical fiber <NUM> to the detector <NUM>. A uniformization member <NUM> is provided between each of the light outputting ends <NUM> of the optical fiber parts 330a to 330e and a corresponding one of the light entry ends <NUM> of the optical fibers <NUM>. The uniformization member <NUM> uniformizes an intensity distribution of light outputted from the light outputting end <NUM>. The uniformization member <NUM> is a member that causes light having entered from a light entry surface <NUM> to be reflected multiple times inside the uniformization member <NUM>. The uniformization member <NUM> is a rod homogenizer having the shape of a polygonal prism.

With reference to <FIG>, the detector <NUM> is provided to each of the optical fibers <NUM> connected to the light applicator <NUM>, and a configuration for connection between the optical fiber <NUM> and the detector <NUM> and a hardware configuration of the detector <NUM> are the same among all the detectors <NUM>. Therefore, one of the detectors <NUM> will be described here. With reference to <FIG>, a hole 22b in which another end <NUM> of the optical fiber <NUM> is inserted, is formed in the detector <NUM>. Here, the light entry end <NUM> of the optical fiber <NUM> is held in a corresponding one of the outlets <NUM> of the light applicator <NUM> (see <FIG>). A holding part 22a for holding a cuvette <NUM>, the hole 22b, and a communication hole 22c are formed in the detector <NUM>. The communication hole 22c allows the hole 22b to be in communication with the holding part 22a.

The diameter of the hole 22b is larger than the diameter of the communication hole 22c. A lens 22d which condenses light from the optical fiber <NUM> is disposed at an end portion of the hole 22b. Further, an opening 22f is formed, in the inner wall surface of the holding part 22a, at a position opposed to the communication hole 22c. Alight reception part <NUM> is disposed behind the opening 22f. The light reception part <NUM> is a photodiode and outputs an electric signal corresponding to the amount of received light. The light transmitted through the lens 22d enters a light reception surface of the light reception part <NUM> via the communication hole 22c, the holding part 22a, and the opening 22f. The optical fiber <NUM> is fixed by a plate spring 22e in a state where the other end <NUM> is inserted in the hole 22b.

With reference to <FIG>, when a cuvette <NUM> is held by the holding part 22a, the light condensed by the lens 22d is transmitted through the cuvette <NUM> and a sample accommodated in the cuvette <NUM> and enters the light reception part <NUM>. If a coagulation reaction progresses in the sample, the turbidity of the sample is increased. In association with this increase, the amount of light that is transmitted through the sample (transmitted light amount) is reduced, whereby the level of an electric signal that is outputted from the light reception part <NUM> is reduced. The electric signal outputted from the light reception part <NUM> is converted into a digital signal by an A/D converter <NUM>, and the digital signal is transmitted to the controller <NUM>. The signal outputted from the light reception part <NUM> and converted by the A/D converter <NUM> is optical information reflecting the transmitted light amount.

Although the light reception part <NUM> of the detector <NUM> detects transmitted light in the above example, light scattered by the sample accommodated in the cuvette <NUM> (scattered light) may be received in the detector <NUM>. In this case, the controller <NUM> analyzes the coagulation reaction on the basis of a change in the intensity of the scattered light. The detector <NUM> which detects scattered light has a configuration in which: an opening is provided in the inner surface of the holding part 22a so as to be located at the same height as that of the communication hole 22c; and a light detector is disposed behind the opening. When the cuvette <NUM> is held by the holding part 22a and light is applied to the cuvette <NUM>, light having been scattered by the sample in the cuvette <NUM> is applied to the light detector via the opening. A detected signal from the light detector indicates the intensity of the scattered light having been scattered by the sample.

With reference to <FIG>, the sample preparation part <NUM> will be described. Each of reagent tables <NUM> and <NUM> and a cuvette table <NUM> has an annular shape and is rotatably configured. The reagent tables <NUM> and <NUM> corresponds to reagent accommodating parts on which reagent containers 81a and 81b and the like are placed. A barcode label having a barcode printed thereon is pasted on each of the reagent containers 81a and 81b and the like. The barcode includes: the type of an accommodated reagent; and a reagent ID which is a serial number assigned to the reagent. The barcode on each of the reagent containers 81a and 81b placed on the reagent tables <NUM> and/or <NUM> is read by a barcode reader <NUM>. The information (the type and the reagent ID of the reagent) read from the barcode is inputted to the controller <NUM> and stored in the storage <NUM> (see <FIG>). The reagent container 81a in which an APTT measurement reagent is accommodated and the reagent container 81b in which a calcium solution is accommodated are placed on the reagent table <NUM> and/or <NUM>.

Support portions 413a which are a plurality of openings capable of supporting cuvettes 80a and 80b and the like are formed in the cuvette table <NUM>. The cuvettes 80a and 80b and the like having been newly set in a cuvette supply part <NUM> by a user are sequentially transferred by the cuvette supply part <NUM> and disposed in corresponding ones of the support portions 413a of the cuvette table <NUM> by a cuvette transfer part <NUM>. The cuvettes 80a and 80b and the like have structures identical to one another.

A specimen dispensing arm <NUM> and a reagent dispensing arm <NUM> respectively have stepping motors connected thereto, so as to be movable upward and downward and so as to be rotatably movable. A pipette 417a having a tip that is sharply formed so as to be capable of puncturing a lid of a specimen container is disposed at the distal end of the specimen dispensing arm <NUM>. A pipette 418a is disposed at the distal end of the reagent dispensing arm <NUM>. A tip of the pipette 418a is flatly formed unlike the tip of the pipette 417a.

A heating part <NUM> includes a plurality of heat openings 424a and is configured to heat a sample accommodated in each of the cuvettes 80a and 80b and the like having been set in corresponding ones of the heat openings 424a. A cuvette transfer part <NUM> includes a catcher 423a for holding the cuvettes 80a and 80b and the like and is configured to transfer the cuvettes 80a and 80b and the like on the cuvette table <NUM> to corresponding ones of the heat openings 424a of the heating part <NUM> and corresponding ones of the holding parts 22a of the detector <NUM>.

As the measurement device <NUM>, a device described in <CIT> can be used.

A measurement process by the measurement device <NUM> is performed under the control of the controller <NUM>, and an analysis process by the analyzer <NUM> is performed under the control of the controller <NUM>. However, the present disclosure is not limited to this example. For example, the measurement process and the analysis process may be performed under the control of the controller <NUM>, or the measurement process and the analysis process may be performed under the control of the controller <NUM>.

With reference to <FIG>, in step S11, the controller <NUM> receives a measurement starting instruction which has been inputted through the input device <NUM> by a user. In step S12, the controller <NUM> transmits instruction data of the measurement starting instruction to the controller <NUM> of the measurement device <NUM>. When the controller <NUM> receives the instruction data in step S13, the controller <NUM> executes a measurement process based on the measurement program in step S14. In step S15, the controller <NUM> transmits, to the controller <NUM>, measurement data obtained through the measurement process, to end the process. In step S16, the controller <NUM> receives the measurement data and stores the measurement data in the storage <NUM>. In step S17, the controller <NUM> executes an analysis process on the measurement data. In step S18, the controller <NUM> outputs an analysis result to the output device <NUM>. In step S18, the controller <NUM> also stores the analysis result in the storage <NUM>.

In step S14 of the measurement process, two samples are prepared from one blood specimen by using the same APTT measurement reagent, and a coagulation time of each of the samples is measured (that is, coagulation time measurement is performed two times). A waiting time from mixing of the blood specimen and the APTT measurement reagent to adding of a calcium solution differs between the two times of measurements. Specifically, the calcium solution is added to a first sample resulting from an elapse of a first waiting time from mixing of the blood specimen from the subject and the APTT measurement reagent, and a first coagulation time is measured. In addition, the calcium solution is added to a second sample resulting from an elapse of a second waiting time from mixing of the blood specimen and the APTT measurement reagent, and a second coagulation time is measured. Here, the second waiting time is a time longer than the first waiting time. The first and second waiting times will be described later. During the first and second waiting times, the first and second samples are respectively incubated. Incubation of the first and second samples is performed at a fixed temperature determined from, for example, a range of not lower than <NUM> and not higher than <NUM>. Incubation of the first and second samples is preferably performed at <NUM>.

The APTT measurement reagent refers to a reagent containing an activator and a phospholipid. The activator refers to a substance that activates a contact factor in the intrinsic coagulation pathway. Examples of the activator include an ellagic acid compound, silica, kaolin, Celite, and the like. The ellagic acid compound may be any of ellagic acid, an ellagic acid salt, and a metal complex of ellagic acid. These types of activators may be used singly, or two or more of these types of activators may be used in combination. The ellagic acid compound is preferably used as the activator. The ellagic acid compound is particularly preferably a metal complex of ellagic acid, containing metal ions such as zinc ions, manganese ions, or aluminum ions. Examples of the phospholipid include phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylserine (PS). The APTT measurement reagent contains one type of phospholipid selected from among PE, PC, and PS, preferably contains two types of phospholipids selected from among PE, PC, and PS, and more preferably contains all of these types of phospholipids. The phospholipid may be a naturally occurring phospholipid or a synthetic phospholipid.

As the APTT measurement reagent, commercially available reagents such as Revohem (registered trademark) APTT SLA (Sysmex Corporation), Thrombocheck (registered trademark) APTT SLA (Sysmex Corporation), Coagpia (registered trademark) APTT-N (Sekisui Medical Co. ), and Data-fi APTT (Siemens Healthcare Diagnostics Products GmbH), may be used.

The calcium solution is a reagent for starting blood coagulation by supplying calcium ions to a mixture of a blood specimen and the APTT measurement reagent. The calcium solution can be a calcium ion-containing aqueous solution. A preferable calcium solution is an aqueous solution of a calcium salt such as calcium chloride. The concentration of the calcium ions in the calcium solution is, for example, not lower than <NUM> and not higher than <NUM>, and preferably <NUM> or <NUM>. If a calcium salt easily soluble in water such as calcium chloride is used, the concentration of the calcium ions in the calcium solution can be expressed as the concentration of the calcium salt.

When step S11 shown in <FIG> is started, the controller <NUM> reads out the first and second waiting times in step S101 with reference to <FIG>. In the present embodiment, the first and second waiting times are prestored in the solid-state drive of the controller <NUM>, the first waiting time is <NUM> seconds, and the second waiting time is <NUM> seconds. Regarding the waiting times, input thereof may be received from a user through the input device <NUM>, or the waiting times may be obtained via the network <NUM> from, for example, an electronic medical chart system <NUM> in a medical institution.

The first and second waiting times may be changed according to, for example, the type of the APTT measurement reagent. For example, each of the first and second waiting times may be determined from a range of not shorter than <NUM> seconds and shorter than <NUM> seconds. The first waiting time is, for example, not shorter than <NUM> seconds and not longer than <NUM> seconds. The second waiting time is, for example, longer than <NUM> seconds and not longer than <NUM> seconds and is longer than the first waiting time by at least <NUM> seconds. More specifically, the first waiting time can be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> seconds. Meanwhile, the second waiting time can be a time that is selected from among <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> seconds and that is longer than the first waiting time by at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> seconds.

Alternatively, each of the first and second waiting times may be determined from a range of longer than <NUM> seconds and not longer than <NUM> seconds. The first waiting time is, for example, longer than <NUM> seconds and not longer than <NUM> seconds. The second waiting time is, for example, longer than <NUM> seconds and not longer than <NUM> seconds and is longer than the first waiting time by at least <NUM> seconds. More specifically, the first waiting time can be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> seconds. Meanwhile, the second waiting time can be a time that is selected from among <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> seconds and that is longer than the first waiting time by at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> seconds.

With reference to <FIG> and <FIG>, in step S102, the controller <NUM> controls the sample preparation part <NUM> to prepare a first sample and add the calcium solution to the prepared first sample. By this control, the pipette 417a of the specimen dispensing arm <NUM> suctions a blood specimen (plasma), from a subject, in a specimen container and dispenses the blood specimen into the cuvette 80a, which is empty, on the cuvette table <NUM>. Then, the cuvette table <NUM> is rotated, the cuvette transfer part <NUM> transfers, to the heating part <NUM>, the cuvette 80a containing the blood specimen from the subject, and the blood specimen in the cuvette 80a is heated to a predetermined temperature (<NUM>). Then, the cuvette transfer part <NUM> transfers the cuvette 80a into a range within which the pipette 418a of the reagent dispensing arm <NUM> is movable, and the pipette 418a adds, into the cuvette 80a, the APTT measurement reagent suctioned from the reagent container 81a. Consequently, a first sample is prepared. The cuvette transfer part <NUM> returns the cuvette 80a to the heating part <NUM>. Immediately before the first waiting time elapses from the adding of the APTT measurement reagent into the cuvette 80a, the cuvette transfer part <NUM> transfers, into the range within which the pipette 418a is movable, the cuvette 80a into which the APTT measurement reagent has been added. Then, after the first waiting time has elapsed from the adding of the APTT measurement reagent, the pipette 418a adds, into the cuvette 80a, the calcium solution suctioned from the reagent container 81b. Immediately after the adding of the calcium solution, the cuvette transfer part <NUM> transfers, into any of the holding parts 22a of the detector <NUM>, the cuvette 80a into which the calcium solution has been added.

With reference to <FIG>, <FIG>, <FIG>, and <FIG>, in step S103, the controller <NUM> controls the measurement device <NUM> to obtain measurement data of the first sample (first measurement data). By this control, the light applicator <NUM> applies light to the cuvette 80a transferred into the holding part 22a. In this example, only the first light source <NUM> applies light. The detector <NUM> transmits, to the controller <NUM>, digital data corresponding to the intensity of received light. Specifically, the light reception part <NUM> outputs an analog signal corresponding to the intensity of the light received via the cuvette 80a and the sample in the cuvette 80a (transmitted light intensity), this signal is converted into a digital signal by the A/D converter <NUM>, and the digital signal is transmitted to the controller <NUM>. The controller <NUM> continues to receive digital data from the time point of start of light application to the cuvette 80a until arrival at a predetermined measurement time (<NUM> seconds). The time from the adding of the calcium solution to the cuvette 80a to the start of the light application is a time shorter than the first waiting time and the second waiting time (for example, shorter than <NUM> second), and thus the time point of the adding of the calcium solution to the cuvette 80a and the time point of the start of the light application can be regarded as substantially the same time point. The controller <NUM> associates a set of continuously received digital data with times having elapsed from the time point of the start of the light application to the cuvette 80a, and stores the associated data as measurement data of the first sample (first measurement data). A time interval at which the controller <NUM> receives the digital data is, for example, <NUM> seconds to <NUM> seconds. With reference to <FIG>, the measurement data is a set of two-dimensional array data including: an upper row indicating transmitted light intensities; and a lower row indicating times at which the respective transmitted light intensities are obtained (the times having elapsed from the time point of the start of the light application to the cuvette <NUM>).

With reference to <FIG> and <FIG>, in step S104, the controller <NUM> controls the sample preparation part <NUM> to prepare a second sample and add the calcium solution to the prepared second sample. By this control, the pipette 417a of the specimen dispensing arm <NUM> suctions the blood specimen (plasma), from the subject, in the specimen container and dispenses the blood specimen into the cuvette 80b, which is empty, on the cuvette table <NUM>. Then, the cuvette table <NUM> is rotated, the cuvette transfer part <NUM> transfers, to the heating part <NUM>, the cuvette 80b containing the blood specimen from the subject, and the blood specimen in the cuvette 80b is heated to the predetermined temperature (<NUM>). Then, the cuvette transfer part <NUM> transfers the cuvette 80b into the range within which the pipette 418a of the reagent dispensing arm <NUM> is movable, and the pipette 418a adds, into the cuvette 80b, the APTT measurement reagent suctioned from the reagent container 81a. Consequently, a second sample is prepared. The cuvette transfer part <NUM> returns the cuvette 80b to the heating part <NUM>. Immediately before the second waiting time elapses from the adding of the APTT measurement reagent into the cuvette 80b, the cuvette transfer part <NUM> transfers, into the range within which the pipette 418a is movable, the cuvette 80b into which the APTT measurement reagent has been added. Then, after the second waiting time has elapsed from the adding of the APTT measurement reagent, the pipette 418a adds, into the cuvette 80b, the calcium solution suctioned from the reagent container 81b. Immediately after the adding of the calcium solution, the cuvette transfer part <NUM> transfers, into any of the holding parts 22a of the detector <NUM>, the cuvette 80b into which the calcium solution has been added. The time from adding of the calcium solution to the cuvette to completion of transfer of the cuvette to the holding part 22a of the detector <NUM> is the same between the first sample and the second sample.

With reference to <FIG>, <FIG>, <FIG>, and <FIG>, in step S105, the controller <NUM> controls the measurement device <NUM> to obtain measurement data of the second sample (second measurement data). By this control, the light applicator <NUM> applies light to the cuvette 80b transferred into the holding part 22a. In this example, only the first light source <NUM> applies light. The detector <NUM> transmits, to the controller <NUM>, digital data corresponding to the intensity of received light. The controller <NUM> continues to receive digital data from the time point of the adding of the calcium solution into the cuvette 80b until arrival at the predetermined measurement time (<NUM> seconds). The controller <NUM> associates a set of continuously received digital data with times having elapsed from the time point of the start of the light application to the cuvette 80b, and stores the associated data as measurement data of the second sample (second measurement data). The data structure of the second measurement data is the same as that of the first measurement data. When processing in step S105 is ended, the controller <NUM> advances the process to step S15. As described above, in step S15, the controller <NUM> transmits the measurement data obtained through the measurement process to the controller <NUM>, and, in step S16, the controller <NUM> receives the measurement data and stores the measurement data in the storage <NUM>.

When step S17 shown in <FIG> is started, the controller <NUM> reads out the measurement data (the first measurement data and the second measurement data) stored in the storage <NUM>, in step S201 with reference to <FIG>. The controller <NUM> plots the read-out first measurement data onto a two-dimensional graph having: a vertical axis (Y axis) indicating the transmitted light intensity; and a horizontal axis (X axis) indicating the measurement time (seconds: sec) over which the transmitted light intensity is monitored. Consequently, the controller <NUM> obtains a first coagulation waveform as shown in <FIG>. Further, the controller <NUM> normalizes the obtained first coagulation waveform. With reference to <FIG>, in the normalized first coagulation waveform, each transmitted light intensity included in the first measurement data is expressed as a relative value so as to be shown between <NUM>% (L1: baseline) and <NUM>% (L2) of the vertical axis. Regarding the second measurement data as well, the controller <NUM> obtains a second coagulation waveform and normalizes the obtained second coagulation waveform in the same manner.

In step S202, the controller <NUM> differentiates the normalized first coagulation waveform to obtain a first-order differential curve of the coagulation waveform as shown in <FIG>. The controller <NUM> further differentiates the first-order differential curve to obtain a second-order differential curve of the coagulation waveform as shown in <FIG>. Regarding the second measurement data as well, the controller <NUM> obtains a first-order differential curve of the corresponding coagulation waveform and a second-order differential curve of the corresponding coagulation waveform in the same manner. In step S201, normalization of the coagulation waveforms can be omitted. In this case, the controller <NUM> obtains a first-order differential curve by differentiating the coagulation waveform not having been normalized (see <FIG>). Although the first-order differential curve is expressed such that a coagulation speed (dT/dt) takes positive values in <FIG>, the first-order differential curve may be expressed such that the coagulation speed takes negative values. The same applies to the second-order differential curve. That is, curves with positive and negative values thereof in the vertical axis being inverted from those of the curves in <FIG>, may be obtained.

In step S203, the controller <NUM> obtains a first coagulation time and a first parameter regarding either of the differentials of the first coagulation waveform (hereinafter, referred to as "first parameter"), for the first sample, and obtains a second coagulation time and a second parameter regarding either of the differentials of the second coagulation waveform (hereinafter, referred to as "second parameter"), for the second sample. Each of the first coagulation time and the second coagulation time is, for example, a time from the adding of the calcium solution to the corresponding sample obtained by mixing of the blood specimen and the APTT measurement reagent to attainment of a predetermined coagulation state. Each of the first and second parameters is a parameter obtained from the first-order differential curve or the second-order differential curve of the corresponding coagulation waveform. The parameter obtained from the first-order differential curve is a value regarding a coagulation speed, and the parameter obtained from the second-order differential curve is a value regarding a coagulation acceleration or a coagulation deceleration.

With reference to <FIG>, obtainment of a first coagulation time tc will be described. In the first coagulation waveform obtained in step S201, a time tI is a time point at which the calcium solution has been added to the sample, and fibrin deposition has not occurred at the time tI. Therefore, the transmitted light intensity takes a high value at the time tI. Thereafter, when a coagulation reaction progresses and fibrin deposition starts, deposited fibrin blocks the light so that the transmitted light intensity starts to be reduced. This time point is a time tII which is a coagulation reaction start time. The controller <NUM> obtains, through an arithmetic operation, a time at which the transmitted light intensity starts to be reduced in the coagulation waveform. The controller <NUM> sets this time as the time tII. The controller <NUM> sets, as <NUM>%, the amount of change in the transmitted light intensity at the time tII.

Thereafter, as fibrin deposition progresses, the transmitted light intensity is further reduced. When most of fibrinogen in the sample turn into fibrin, the reaction converges so that the coagulation waveform plateaus. The controller <NUM> obtains, through an arithmetic operation, a time at which the coagulation waveform starts to plateau. The controller <NUM> sets this time as a time tIII. The time tIII is a coagulation reaction end time. The controller <NUM> sets, as <NUM>%, the amount of change in the transmitted light intensity at the time tIII. Then, the controller <NUM> sets, as a time tc, a time at which the amount of change in the transmitted light intensity is <NUM>% (a time at an intersection point between a line L3 and the coagulation waveform). The controller <NUM> obtains this time as the first coagulation time. The coagulation time is not limited to a time at which the amount of change in the transmitted light intensity is <NUM>%, and a time at which the amount of change is an arbitrarily-selected value such as <NUM>%, <NUM>%, <NUM>%, or <NUM>% may be obtained as the coagulation time. Alternatively, the coagulation time (time tc) may be, for example, a time after a constant time counted from the time tII which is the coagulation reaction start time. If normalization of the coagulation waveform is omitted, the controller <NUM> obtains the first coagulation time tc from the coagulation waveform not having been normalized. The controller <NUM> also obtains the second coagulation time on the basis of the second coagulation waveform through the same method as that for the first coagulation time tc.

In step S203, the controller <NUM> obtains, through an arithmetic operation, the first parameter on the basis of the first-order differential curve and/or the second-order differential curve, of the first coagulation waveform, which have been obtained in step S202. Examples of the first parameter include, but are not limited to, |min <NUM>|, |min <NUM>|, |max <NUM>|, a maximum speed arrival time (tmin1), a maximum acceleration arrival time (tmin2), and the like. As shown in <FIG>, |min <NUM>| is the absolute value of a peak value (min1) of the coagulation speed in the first-order differential curve and indicates a maximum coagulation speed. tmin1 is a time from the coagulation reaction start time (time tII) to arrival at the maximum coagulation speed, in the first-order differential curve. As shown in <FIG>, |min <NUM>| is the absolute value of a peak value of the coagulation acceleration in the second-order differential curve and indicates a maximum coagulation acceleration. |max <NUM>| is the absolute value of a peak value (min2) of the coagulation deceleration in the second-order differential curve and indicates a maximum coagulation deceleration. tmin2 is a time from the coagulation reaction start time (time tII) to arrival at the maximum coagulation acceleration, in the second-order differential curve. The controller <NUM> also obtains the second parameter on the basis of the first-order differential curve and/or the second-order differential curve of the second coagulation waveform through the same method as that for the first parameter. In the present embodiment, obtainment of the first-order differential curve and the second-order differential curve in step S202, and obtainment of the first and second parameters in step S203, may be omitted.

In S204, the controller <NUM> obtains at least one index value based on the coagulation times and/or the parameters obtained in step S203. This index value is a value that is changed according to the cause of coagulation time prolongation. For example, the index value can indicate that the blood specimen from the subject is suspected of containing LA or heparin. Alternatively, the index value can indicate that the blood specimen from the subject is suspected of containing heparin. Alternatively, the index value can indicate that the blood specimen from the subject is suspected of having a cause of prolongation other than LA and heparin.

The controller <NUM> obtains, through an arithmetic operation, an index value by using the coagulation times and/or the values of the parameters obtained in step S203. Mathematical expressions for calculating the index value are stored in the function database DB1 (<FIG>). An index value <NUM> as an example of the index value is, for example, a value calculated by using the following mathematical expression <NUM>. In the mathematical expression, "-" indicates subtraction.

In step S205, the controller <NUM> compares the index value obtained in step S204 and a predetermined threshold value with each other, and determines a cause of prolonging the coagulation reaction. The predetermined threshold value is a reference value according to which a cause of coagulation time prolongation of the blood specimen is determined. The predetermined threshold value is stored in the threshold value database DB2 (<FIG>) of the storage <NUM>. A determination result for the cause of prolonging the coagulation reaction is outputted by the output device <NUM> in step S18 (<FIG>).

The predetermined threshold value is preset correspondingly to the mathematical expression. For example, if a first index value is a value obtained by subtracting the second coagulation time from the first coagulation time (the value calculated by using the mathematical expression <NUM>), this value and a first threshold value are compared with each other.

With reference to <FIG>, a comparison process in step S205 will be described. In step S301, the first index value and the first threshold value are compared with each other, and, in a case where the first index value is not lower than the first threshold value (in the case of "NO"), the controller <NUM> advances the process to step S302 in which the controller <NUM> determines that the blood specimen is suspected of containing LA or heparin. In step S301, in a case where the first index value is lower than the first threshold value (in the case of "YES"), the controller <NUM> advances the process to step S303 in which the controller <NUM> determines that the blood specimen is suspected of having a cause of prolongation other than LA and heparin. For example, in a case where the first coagulation time is a coagulation time of a sample for which the waiting time is <NUM> seconds, and the second coagulation time is a coagulation time of a sample for which the waiting time is <NUM> seconds, the first threshold value may be <NUM> seconds. The first index value may be calculated by using the following mathematical expression <NUM> instead of the mathematical expression <NUM>.

Hereinafter, modifications of the comparison process in step S205 will be described. An index value <NUM> as an example of the index value can be, for example, a value calculated by using the following mathematical expression <NUM>. In the mathematical expression, "-" indicates subtraction. In the present embodiment, each of the first parameter and the second parameter is |min <NUM>|.

A predetermined threshold value is preset according to the mathematical expression. For example, if a second index value is a value obtained by subtracting the value of the second parameter from the value of the first parameter (the value calculated by using the mathematical expression <NUM>), this value and a second threshold value are compared with each other.

With reference to <FIG>, in step S401, the second index value and the second threshold value are compared with each other, and, in a case where the second index value is not lower than the second threshold value (in the case of "NO"), the controller <NUM> advances the process to step S402 in which the controller <NUM> determines that the blood specimen is suspected of containing LA or heparin. In step S401, in a case where the second index value is lower than the second threshold value (in the case of "YES"), the controller <NUM> advances the process to step S403 in which the controller <NUM> determines that the blood specimen is suspected of having a cause of prolongation other than LA and heparin. The second index value may be calculated by using the following mathematical expression <NUM> instead of the mathematical expression <NUM>.

The index value is not limited to the values calculated by using mathematical expressions exemplified by the mathematical expressions <NUM> to <NUM>. The index value can be, for example, any of values calculated by using the following mathematical expressions. In the mathematical expressions, "/" indicates division. <MAT> <MAT> <MAT> <MAT>.

Further modifications of the index values calculated by using the above mathematical expressions may be, for example, a value obtained by multiplying, by a constant, a value calculated by using any of the above mathematical expressions <NUM> to <NUM>, a value obtained by adding a constant to a value calculated by using any of the above mathematical expressions, a value obtained by subtracting a constant from a value calculated by using any of the above mathematical expressions, a reciprocal of a value calculated by using any of the above mathematical expressions, a value obtained by combining these calculations, and the like. The constant is not particularly limited and can be, for example, an arbitrarily-selected natural number. Alternatively, the value of a coagulation time, of the blood specimen from the subject, obtained in ordinary APTT measurement (with a waiting time of, for example, <NUM> seconds) may be used as the constant.

Predetermined threshold values corresponding to the respective index values are not particularly limited. For example, the predetermined threshold values can be empirically set by obtaining first and second coagulation times and first and second parameters and accumulating data of index values for specimens having known causes of coagulation time prolongation, such as LA-positive specimens, heparin-containing specimens, coagulation factor-deficient specimens, warfarin-containing specimens, and DOAC-containing specimens. Alternatively, index values may be obtained for each of an LA-positive specimen group, a heparin-containing specimen group, and specimen groups having causes of prolongation other than LA and heparin, and a value that enables clear distinction between these groups may be set as a predetermined threshold value. A method for setting the threshold values is not particularly limited, and the threshold values may be set through, for example, ROC analysis. In threshold value setting performed through ROC analysis, ROC curves among which threshold value candidates differ may be drawn on a graph having a vertical axis indicating sensitivity and a horizontal axis indicating <NUM>-specificity, and a threshold value candidate corresponding to a point on the ROC curve closest to a point at which the sensitivity is <NUM> and the <NUM>-specificity is <NUM>, may be set as a predetermined threshold value.

The first and second waiting times do not need to be <NUM> seconds and <NUM> seconds, and can be various times as described above. Hereinafter, a case where each of the first and second waiting times is longer than <NUM> seconds and not longer than <NUM> seconds (for example, the first waiting time is <NUM> seconds, and the second waiting time is <NUM> seconds) will be described as an example.

<FIG> shows a comparison process in a case where: each of the first and second waiting times is longer than <NUM> seconds and not longer than <NUM> seconds (for example, the first waiting time is <NUM> seconds, and the second waiting time is <NUM> seconds); and a third index value is the value of the ratio of the first coagulation time to the second coagulation time (the value calculated by using the mathematical expression <NUM>). In step S501, the third index value and a third threshold value are compared with each other, and, in a case where the third index value is lower than the third threshold value (in the case of "YES"), the controller <NUM> advances the process to step S502 in which the controller <NUM> determines that the blood specimen is suspected of containing heparin. In step S501, in a case where the third index value is not lower than the third threshold value (in the case of "NO"), the controller <NUM> advances the process to step S503 in which the controller <NUM> determines that the blood specimen is suspected of having a cause of prolongation other than heparin.

<FIG> shows a comparison process in a case where: each of the first and second waiting times is longer than <NUM> seconds and not longer than <NUM> seconds (for example, the first waiting time is <NUM> seconds, and the second waiting time is <NUM> seconds); and a fourth index value is the value of the ratio of the value of the first parameter to the value of the second parameter (the value calculated by using the mathematical expression <NUM>). In step S601, the fourth index value and a fourth threshold value are compared with each other, and, in a case where the fourth index value is lower than the fourth threshold value (in the case of "YES"), the controller <NUM> advances the process to step S602 in which the controller <NUM> determines that the blood specimen is suspected of containing LA or heparin. In step S601, in a case where the fourth index value is not lower than the fourth threshold value (in the case of "NO"), the controller <NUM> advances the process to step S603 in which the controller <NUM> determines that the blood specimen is suspected of having a cause of prolongation other than LA and heparin.

A comparison process in a case of having obtained two index values will be described. <FIG> shows a comparison process in a case where: each of the first and second waiting times is longer than <NUM> seconds and not longer than <NUM> seconds (for example, the first waiting time is <NUM> seconds, and the second waiting time is <NUM> seconds); the third index value is the value of the ratio of the first coagulation time to the second coagulation time (the value calculated by using the mathematical expression <NUM>); and the fourth index value is the value of the ratio of the value of the first parameter to the value of the second parameter (the value calculated by using the mathematical expression <NUM>). In step S701, the third index value and the third threshold value are compared with each other, and, in the case where the third index value is lower than the third threshold value (in the case of "NO"), the controller <NUM> advances the process to step S702 in which the controller <NUM> determines that the blood specimen is suspected of containing heparin. In step S701, in the case where the third index value is not lower than the third threshold value (in the case of "YES"), the controller <NUM> advances the process to step S703.

In step S703, the fourth index value and the fourth threshold value are compared with each other, and, in the case where the fourth index value is lower than the fourth threshold value (in the case of "NO"), the controller <NUM> advances the process to step S704 in which the controller <NUM> determines that the blood specimen is suspected of containing LA. In step S703, in the case where the fourth index value is not lower than the fourth threshold value (in the case of "YES"), the controller <NUM> advances the process to step S705 in which the controller <NUM> determines that the blood specimen is suspected of having a cause of prolongation other than LA and heparin.

When the processing in step S205 is completed, the controller <NUM> returns the process to step S18 (<FIG>), outputs a result of the comparison process to the output device <NUM> as information regarding a cause of coagulation time prolongation, and stores the result in the storage <NUM>. In the case where the comparison result in step S301 is "YES", in the case where the comparison result in step S401 is "YES", in the case where the comparison result in step S601 is "NO", and in the case where the comparison result in step S703 is "YES", the result of the comparison process outputted to the output device <NUM> may be, for example, "suspicion of having a cause of prolongation other than mixing of LA and mixing of heparin". In the case where the comparison result in step S501 is "NO", the result of the comparison process outputted to the output device <NUM> may be, for example, "suspicion of having a cause of prolongation other than mixing of heparin". In the case where the comparison result in step S301 is "NO", in the case where the comparison result in step S401 is "NO", and in the case where the comparison result in step S601 is "YES", the result of the comparison process outputted to the output device <NUM> may be, for example, "suspicion of mixing of LA or heparin". In the case where the comparison result in step S501 is "YES" and in the case where the comparison result in step S701 is "NO", the result of the comparison process outputted to the output device <NUM> may be, for example, "suspicion of mixing of heparin". In the case where the comparison result in step S703 is "NO", the result of the comparison process outputted to the output device <NUM> may be, for example, "suspicion of LA". The result of the comparison process outputted to the output device <NUM> may be, for example, displayed as characters such as "suspicion of LA" or "suspicion of mixing of heparin", or as a pictorial mark or a symbol such as a flag.

With reference to <FIG> and <FIG>, in step S18, the controller <NUM> may output, as information regarding a cause of coagulation time prolongation, the index value obtained in step S204 to the output device <NUM> without performing step S205. Alternatively, in step S18, the controller <NUM> may output, as information regarding a cause of coagulation time prolongation, the index value obtained in step S204 to the output device <NUM> also in the case of performing step S205. Alternatively, in step S18, the controller <NUM> may output, as information regarding a cause of coagulation time prolongation, the index value obtained in step S204 and the result of the comparison process obtained in step S205.

In the measurement process, four samples are prepared from the one blood specimen by using the same APTT measurement reagent, and a coagulation time of each of the samples is measured (that is, coagulation time measurement is performed four times). Specifically, measurement of a third coagulation time and a fourth coagulation time is performed in addition to measurement of the first and second coagulation times. In this case, the calcium solution is added to a third sample resulting from an elapse of a third waiting time from mixing of the blood specimen from the subject and the APTT measurement reagent, and the third coagulation time is measured. In addition, the calcium solution is added to a fourth sample resulting from an elapse of a fourth waiting time from mixing of the blood specimen and the APTT measurement reagent, and the fourth coagulation time is measured. Here, the third waiting time is a time longer than the second waiting time, and the fourth waiting time is a time longer than the third waiting time. The incubation temperature for the third and fourth samples is the same as the incubation temperature for the first and second samples.

In the above modification, at least one of the first and second waiting times is shorter than a waiting time in ordinary APTT measurement, and the third and fourth waiting times are longer than the waiting time in ordinary APTT measurement. Specifically, each of the first and second waiting times is determined from a range of not shorter than <NUM> seconds and shorter than <NUM> seconds, and each of the third and fourth waiting times is determined from a range of longer than <NUM> seconds and not longer than <NUM> seconds. The first waiting time is, for example, not shorter than <NUM> seconds and not longer than <NUM> seconds. The second waiting time is, for example, longer than <NUM> seconds and not longer than <NUM> seconds and is longer than the first waiting time by at least <NUM> seconds. The third waiting time is, for example, longer than <NUM> seconds and not longer than <NUM> seconds. The fourth waiting time is, for example, longer than <NUM> seconds and not longer than <NUM> seconds and is longer than the third waiting time by at least <NUM> seconds. The same descriptions as those made above regarding the first and second waiting times apply to more detailed exemplification of each of the waiting times.

With reference to <FIG>, a measurement process in the above modification will be described. In step S111, the controller <NUM> reads out the first to fourth waiting times. From step S112 to step S115, the controller <NUM> executes the same process as that from step S102 to step S105. In step S116, the controller <NUM> performs the same processing as that in step S102 such that a third sample is prepared by adding the APTT measurement reagent to the blood specimen. In addition, in step S116, the controller <NUM> controls the sample preparation part <NUM> to add the calcium solution to the third sample after the third waiting time has elapsed from the adding of the APTT measurement reagent. In step S117, the controller <NUM> performs the same processing as that in step S103 such that measurement data of the third sample (third measurement data) is obtained from the third sample to which the calcium solution has been added in step S116. In step S118, the controller <NUM> performs the same processing as that in step S102 such that a fourth sample is prepared by adding the APTT measurement reagent to the blood specimen. In addition, in step S118, the controller <NUM> controls the sample preparation part <NUM> to add the calcium solution to the fourth sample after the fourth waiting time has elapsed from the adding of the APTT measurement reagent. In step S119, the controller <NUM> performs the same processing as that in step S103 such that measurement data of the fourth sample (fourth measurement data) is obtained from the fourth sample to which the calcium solution has been added in step S118.

With reference to <FIG>, an analysis process in the above modification will be described. In step S211, the controller <NUM> performs the same processing as that in step S201 such that coagulation waveforms of the respective first, second, third, and fourth samples are obtained and normalized. In step S212, the controller <NUM> differentiates each of the coagulation waveforms to obtain a first-order differential curve, and differentiates the first-order differential curve to obtain a second-order differential curve. Normalization of the coagulation waveforms in step S211 may be omitted. In this case, the controller <NUM> obtains a first-order differential curve and a second-order differential curve from each of the coagulation waveforms not having been normalized. In step S213, the controller <NUM> performs the same processing as that in step S203 such that: the first coagulation time and the first parameter are obtained for the first sample; the second coagulation time and the second parameter are obtained for the second sample; the third coagulation time and a third parameter regarding either of the differentials of a third coagulation waveform (hereinafter, referred to as "third parameter") are obtained for the third sample; and the fourth coagulation time and a fourth parameter regarding either of the differentials of a fourth coagulation waveform (hereinafter, referred to as "fourth parameter") are obtained for the fourth sample. The third coagulation time and the third parameter are a coagulation time and a parameter regarding either of the differentials of the corresponding coagulation waveform which have been obtained on the basis of the third measurement data of the third sample. The fourth coagulation time and the fourth parameter are a coagulation time and a parameter regarding either of the differentials of the corresponding coagulation waveform which have been obtained on the basis of the fourth measurement data of the fourth sample.

In step S214, the controller <NUM> obtains, through an arithmetic operation, a first index value and a fifth index value which are based on the coagulation times and/or the parameters obtained in step S213. The first index value can be, for example, a value calculated by using any of the above mathematical expressions <NUM> to <NUM>. The fifth index value can be, for example, a value calculated by using any of the following mathematical expressions <NUM> to <NUM>. In the mathematical expressions, "-" indicates subtraction, and "/" indicates division. <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT>.

The first and fifth index values are not limited to the values calculated by using mathematical expressions exemplified by the mathematical expressions <NUM> to <NUM>. Modifications of the index values have been described above. In a preferred embodiment, the first index value is a value calculated by using the mathematical expression <NUM> or <NUM>, and the fifth index value is a value calculated by using the mathematical expression <NUM> or <NUM>.

In step S215, the controller <NUM> compares each of the first and fifth index values and a predetermined threshold value corresponding to the index value with each other. With reference to <FIG>, a comparison process in step S215 will be described. <FIG> shows a comparison process in a case where: the first index value is a value obtained by subtracting the second coagulation time from the first coagulation time (the value calculated by using the mathematical expression <NUM>); and the fifth index value is the value of the ratio of the third coagulation time to the fourth coagulation time (the value calculated by using the mathematical expression <NUM>).

In step S801, the first index value and the first threshold value are compared with each other, and, in a case where the first index value is lower than the first threshold value (in the case of "NO"), the controller <NUM> advances the process to step S802 in which the controller <NUM> determines that the blood specimen is suspected of having a cause of prolongation other than LA and heparin. In step S801, in a case where the first index value is not lower than the first threshold value (in the case of "YES"), the controller <NUM> advances the process to step S803. In step S803, the fifth index value and a fifth threshold value are compared with each other, and, in a case where the fifth index value is not lower than the fifth threshold value (in the case of "NO"), the controller <NUM> advances the process to step S804 in which the controller <NUM> determines that the blood specimen is suspected of containing LA. In step S803, in a case where the fifth index value is lower than the fifth threshold value (in the case of "YES"), the controller <NUM> advances the process to step S805 in which the controller <NUM> determines that the blood specimen is suspected of containing heparin. For example, in a case where the third coagulation time is a coagulation time of a sample for which the waiting time is <NUM> seconds, and the fourth coagulation time is a coagulation time of a sample for which the waiting time is <NUM> seconds, the fifth threshold value may be <NUM>.

Hereinafter, the present disclosure will be described in further detail using Examples. However, the present disclosure is not limited to these Examples.

For each of blood specimens having APTTs prolonged owing to various causes, the manner in which the measured APTT thereof was changed when the time for incubation performed after the blood specimen was mixed with an APTT measurement reagent was changed from a time for incubation performed in ordinary APTT measurement, was examined. In addition, whether distinguishment between causes of prolonging the APTTs was possible on the basis of obtained APTTs, was examined.

Revohem (registered trademark) APTT SLA (Sysmex Corporation) was used as an APTT measurement reagent. This reagent contains ellagic acid and synthetic phospholipid. A <NUM>-mM calcium chloride solution (Sysmex Corporation) was used as a calcium solution. Normal plasmas (<NUM> examples) obtained from healthy individuals, LA-containing plasmas (<NUM> examples) obtained from LA-positive patients, coagulation factor-deficient plasmas (<NUM> examples) obtained from patients deficient in factor VIII or factor IX, heparin-containing plasmas (<NUM> examples) obtained from heparin-administered patients, warfarin-containing plasmas (<NUM> examples) obtained from warfarin-administered patients, and DOAC-containing plasmas (<NUM> examples) obtained from direct oral anticoagulant (DOAC)-administered patients, were used as blood specimens.

Each of the blood specimens (<NUM>µl) was heated at <NUM> for <NUM> minute. Thereafter, the APTT measurement reagent (<NUM>µl) was added to the blood specimen, and the mixture was 3incubated at <NUM> for <NUM> seconds. Then, the calcium solution (<NUM>µl) was added to the mixture of the blood specimen and the APTT measurement reagent, measurement data of transmitted light intensity at a wavelength of <NUM> was obtained for the blood specimen, and a coagulation time was obtained from the obtained measurement data. Therefore, the waiting time from the adding of the APTT measurement reagent to the adding of the calcium solution was <NUM> seconds. All of these operations were performed with a fully automatic coagulation time measurement apparatus CS-<NUM> (Sysmex Corporation). The APTTs of the respective blood specimens have been indicated with a boxplot in <FIG>. As seen from <FIG>, the coagulation times of the blood specimens other than the normal plasmas were prolonged. However, distinguishment between the causes of prolonging the coagulation times of the blood specimens other than the normal plasmas was difficult with only the APTTs.

Each of the blood specimens (<NUM>µl) was heated at <NUM> for <NUM> minute. Thereafter, the APTT measurement reagents (<NUM>µl) were added to the blood specimens, and the mixtures were incubated at <NUM> for <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, and <NUM> seconds. Then, coagulation times of the blood specimens were obtained in the same manner as in the above measurement (<NUM>). Therefore, the waiting times from the adding of the APTT measurement reagent to the adding of the calcium solution were <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, and <NUM> seconds. All of these operations were performed with CS-<NUM>. <FIG> is a graph showing APTTs, at the respective waiting times, of the normal plasma, the LA-containing blood specimen, the coagulation factor-deficient blood specimen, the heparin-containing blood specimen, the warfarin-containing blood specimen, and the DOAC-containing blood specimen. As shown in <FIG>, with the waiting time being shorter than <NUM> seconds, the APTTs of all of the blood specimens tended to be elongated, and the APTTs of the LA-containing blood specimen, the coagulation factor-deficient blood specimen, and the heparin-containing blood specimen tended to be elongated more than the APTTs of the normal plasma, the warfarin-containing blood specimen, and the DOAC-containing blood specimen. Meanwhile, with the waiting time being longer than <NUM> seconds, the APTTs of the normal plasma, the LA-containing blood specimen, the coagulation factor-deficient blood specimen, the DOAC-containing blood specimen, and the warfarin-containing blood specimen tended to be shortened, but the APTTs of the heparin-containing blood specimen tended to be elongated.

Index values each based on APTTs at two different waiting times were obtained for each of the blood specimens in order to quantitatively evaluate a change, in APTT, that occurred according to the change in waiting time. Specifically, the value of the difference ([first APTT]-[second APTT]) between an APTT (first APTT) at a waiting time of <NUM> seconds and an APTT (second APTT) at a waiting time of <NUM> seconds, was calculated. In addition, the value of the ratio ([third APTT]/[fourth APTT]) of an APTT (third APTT) at a waiting time of <NUM> seconds to an APTT (fourth APTT) at a waiting time of <NUM> seconds, was calculated. The values calculated for each of the blood specimens have been indicated with boxplots in <FIG>.

As shown in <FIG>, the difference between the first APTT and the second APTT took a high value for each of the LA-containing plasma and the heparin-containing plasma. This result has indicated that whether the blood specimen is suspected of containing either of LA and heparin or is suspected of having a cause other than LA and heparin (coagulation factor deficiency, warfarin, or DOAC), can be determined on the basis of the value of the difference between the first APTT and the second APTT. Meanwhile, as shown in <FIG>, the ratio of the third APTT to the fourth APTT took a low value for the heparin-containing plasma. This result has indicated that whether the blood specimen is suspected of containing heparin or is suspected of having a cause other than heparin (LA, coagulation factor deficiency, warfarin, or DOAC), can be determined on the basis of the value of the ratio of the third APTT to the fourth APTT. Further, it has been indicated that use of the value of the difference between the first APTT and the second APTT and the value of the ratio of the third APTT to the fourth APTT makes it possible to determine whether the blood specimen is suspected of containing LA, is suspected of containing heparin, or is suspected of having a cause other than LA and heparin.

Whether distinguishment between the causes of prolonging the APTTs was possible also on the basis of parameters regarding differentials of coagulation waveforms obtained through coagulation time measurement with the waiting time being changed, was examined.

Coagulation waveforms and first-order differential curves differentiated therefrom were obtained from time-series datasets regarding each of the blood specimens obtained in Example <NUM>. From each of the first-order differential curves, a maximum coagulation speed (|min <NUM>|) was obtained as a parameter regarding the differential of the corresponding coagulation waveform. The value of the difference ([first |min <NUM>|]-[second |min <NUM>|]) between |min <NUM>| (first |min <NUM>|) at a waiting time of <NUM> seconds and |min <NUM>| (second |min <NUM>|) at a waiting time of <NUM> seconds was calculated in the same manner as in Example <NUM>. In addition, the value of the ratio ([third |min <NUM>|]/[fourth |min <NUM>|]) of |min <NUM>| (third |min <NUM>|) at a waiting time of <NUM> seconds to |min <NUM>| (fourth |min <NUM>|) at a waiting time of <NUM> seconds was calculated. The values calculated for each of the blood specimens have been indicated with boxplots in <FIG>.

Claim 1:
A method for analyzing a cause of prolonging a coagulation time of a blood specimen from a subject, without using a specimen obtained by mixing of the blood specimen from the subject and a normal blood specimen, the method comprising:
adding a calcium solution to a first sample resulting from an elapse of a first waiting time from mixing of the blood specimen from the subject and a measurement reagent for an activated partial thromboplastin time;
obtaining a first coagulation time and/or a first parameter regarding a differential of a coagulation waveform, for the first sample to which the calcium solution has been added;
adding the calcium solution to a second sample resulting from an elapse of a second waiting time, which is longer than the first waiting time, from mixing of the blood specimen from the subject and the measurement reagent;
obtaining a second coagulation time and/or a second parameter regarding a differential of a coagulation waveform, for the second sample to which the calcium solution has been added; and
obtaining information regarding a cause of prolonging a coagulation time, on the basis of the first coagulation time and/or the first parameter and the second coagulation time and/or the second parameter, wherein
the obtaining of the information comprises
obtaining an index value based on the first coagulation time and/or the first parameter and the second coagulation time and/or the second parameter, and
obtaining the information on the basis of a result of comparison between the index value and a predetermined threshold value, and wherein
the information is related to a suspicion that the blood specimen contains lupus anticoagulant when the result of comparison matches a predetermined condition; or
the information is related to a suspicion that the blood specimen contains heparin when the result of comparison matches a predetermined condition; or
the information is related to a suspicion that the blood specimen contains lupus anticoagulant or heparin when the result of comparison matches a predetermined condition.