Patent Description:
Patent Documents <CIT> and <CIT> are considered relevant. <CIT> relates to a device and method for performing a point of care diagnostic test for detecting and quantifying at least one analyte in a biological sample. A device includes an immunoassay apparatus and a holder with an adjustable variable angle stage for positioning the immunoassay apparatus relative to a light source and a detector device so as to optimize the angle of incidence and angle of radiation to optimize an elastic light scattering signal from the immunoassay apparatus.

<CIT> relates to an assay test strip includes a flow path, a sample receiving zone, a label, a detection zone that includes a region of interest, and at least one position marker. The at least one position marker is aligned with respect to the region of interest such that location of the at least one position marker indicates a position of the region of interest.

Lateral flow assay devices <NUM> are well known in the art and are used extensively in the human medical and veterinary fields for testing a blood sample (i.e., whole blood, plasma or serum) or other bodily fluid (e.g. urine, saliva, milk etc.) for the presence, absence or quantity of a one or more target analytes. Target analytes can include, for example, antibodies, antigens, hormones, small molecules, drug residues and the like. When testing for antibodies or antigens, the presence of such markers is typically an indication of an infectious disease in the patient whose blood is being tested. One example of such a lateral flow assay device <NUM> is disclosed in <CIT>. Another example of a lateral flow assay device <NUM>, structured to effect a bi-directional capillary flow of a sample, is disclosed in <CIT>, which issued to Scott M. Clark, the latter patented device being manufactured or distributed by IDEXX Laboratories, Inc. of Westbrook, Maine under the trademark SNAP®. Other examples of lateral flow assays, such as those that use colloidal gold for visual indication of the presence, absence or quantity of a target analyte, are well known and documented in the prior art. The disclosure of each of the aforementioned patents is incorporated herein by reference.

Many such lateral flow assay devices <NUM> exhibit a human perceptible colorimetric change in an exposed viewing or read area of the device <NUM> as an indication of the presence, absence, or quantity of an analyte in the blood sample. In the SNAP® device, a wash buffer and substrate solution are used to enhance the visible perception of color changes in the read area of the device. The wash solution removes any unbound components, sample debris and unreacted conjugate reagent from the flow matrix of the device <NUM>, leaving a substantially clean, white background in the read area of the device <NUM>. The substrate solution causes an enzymatic reaction which results in a distinct blue-colored dot, or dots, in the read area of the device <NUM> that are easy to observe against the background of the white-colored matrix. Lateral flow devices that utilize colloidal gold as a marker typically have a reddish/brown color when the particles accumulate at the test and/or control line.

<FIG> of the drawings is a top view of a portion of a SNAP® 4Dx® Plus lateral flow assay device <NUM> used for screening dogs for six vector-borne diseases. In the read area <NUM> of the device <NUM>, a blue dot <NUM> appearing in the upper section indicates the presence of A. phagocytophilum/A. platys Ab in the sample being tested. The blue dot <NUM> on the right side of the read area <NUM> (when the device <NUM> is viewed from the front) indicates the presence of Heartworm Ag in the sample. A blue dot <NUM> in the lower center portion of the read area <NUM> of the device <NUM> indicates the presence of Lyme disease Ab, and a blue dot <NUM> on the left side of the read area <NUM> (when the device <NUM> is viewed from the front) indicates the presence of E. ewingii Ab. In the upper left corner of the read area <NUM> of the device <NUM>, there is located a positive control spot <NUM> which will turn blue if the device <NUM> is working properly.

There also exists instruments which read the lateral flow assay devices <NUM> and render an evaluation of the tests being performed, rather than having a human visually determine from the indicator or detection dots <NUM>, <NUM>, <NUM>, <NUM> whether the test results are positive or negative. For example, the SNAP® Reader analyzer, manufactured and distributed by IDEXX Laboratories, Inc. , is an image-analysis instrument which includes a digital camera. The analyzer stores and processes images of SNAPS tests according to the protocol of the specific, individual SNAPS tests designed for use with the analyzer. The SNAP® Reader analyzer then uses custom software to evaluate the results of the tests being run and reports the results. The analyzer takes digital pictures as test results are developing, and the software of the analyzer uses algorithms specific to the test to calculate the test results from these digital images. Other analyzers exist for reading lateral flow devices based on colloidal gold technology, such as: DCN Technologies, Carlsbad, California; and the ESEQuant™ lateral flow reader from Qiegen NV, Venlow, Netherlands.

Although prior art assay readers provide a quick and easy, and highly reliable, indication of the presence, absence or quantity of an analyte, in practice, there may be situations when a result may be difficult to discern. For example, with respect to device <NUM>, the blue detection dot or dots <NUM>, <NUM>, <NUM>, <NUM> may not be fully formed; that is, they may be crescent-shaped, rather than completely circular. Or, the dots <NUM>, <NUM>, <NUM>, <NUM> may be intermittently colored, for example, exhibiting blue disconnected speckles. There are times when the detection dots <NUM>, <NUM>, <NUM>, <NUM> may be only lightly colored. Similar situations occur with colloidal gold lateral flow devices. The prior art analyzer's software will apply algorithmic rules to the digital images taken by the camera of the read area which are analyzed, and make determinations as to whether the blood sample tested contains a target analyte, or whether the results are indeterminate and new tests need to be performed. The deterministic rules applied by the analyzer's software in the prior art are generally highly accurate, but are not based on human perception, to which the present invention relates.

It is an object of the present invention to provide an instrument for reading a lateral flow assay device based on human visual perceptions of colorimetric changes in the device.

It is another object of the present invention to provide a method for reading a lateral flow assay device by detecting color changes thereto based on human perception.

It is yet a further object of the present invention to provide a method and instrument for reading a lateral flow assay device which includes a detection zone in which a visually perceptible colorimetric change may occur, the instrument and method comparing images of the detection zone of the assay device against sample readings of human visual perceptions of colorimetric changes of reference assay devices in a stored database to determine whether the assay device detects the presence, absence or quantity of an analyte in a tested fluid sample.

In accordance with one form of the present invention, an instrument for reading a lateral flow assay device is provided. The lateral flow assay device performs an assay to determine the presence, absence or quantity of an analyte in a fluid sample. The assay device is placed in optical proximity to the instrument, and further has a sample deposit zone on which the fluid sample to be tested is placed. The assay device further has a detection zone in which a visually perceptible colorimetric change may occur when the assay device detects the presence, absence or quantity of an analyte in the fluid sample.

The instrument of the present invention includes an optics module. The optics module has at least one camera which is positioned on the instrument to view the detection zone of the assay device placed in optical proximity to the instrument. The at least one camera generates an output signal which is representative of an image of the detection zone of the assay device and which is indicative of a colorimetric change in the detection zone of the assay device.

The instrument of the present invention further includes a signal processor in electrical communication with the optics module. The signal processor receives the output signal from the at least one camera, and converts the signal into measured colorimetric data.

The instrument of the present invention also includes a storage memory that is in electrical communication with the signal processor. The storage memory has stored therein a dataset of sample readings of reference assay devices similar in structure and function to that of the assay device read by the instrument. These sample readings are based on human visual perceptions of colorimetric changes in the detection zones of the reference assay devices.

A comparator circuit, forming part of the instrument of the present invention, is in electrical communication with the signal processor. The comparator circuit compares the measured colorimetric data relating to the assay device read by the instrument with the stored dataset of sample readings based on human visual perceptions of the colorimetric changes of the reference assay devices. Then, the comparator circuit generates a comparison signal in response thereto.

The signal processor receives this comparison signal from the comparator circuit and in response thereto generates a determination signal indicative of the presence, absence or quantity of an analyte in the fluid sample tested by the assay device read by the instrument.

In an alternative embodiment of the present invention, the optics module of the instrument may include at least one light source and a light detector. The at least one light source emits light and is positioned on the instrument to direct the light onto the detection zone of the assay device placed in optical proximity to the instrument. The light detector receives reflected or fluoresced light emanating from the detection zone of the assay device in response to the light directed thereon by the at least one light source. The light detector generates an output signal in response to the reflected or fluoresced light received by the light detector, the output signal being indicative of a colorimetric change in the detection zone of the assay device. This output signal is provided to the signal processor of the instrument.

As stated previously, a method for reading a lateral flow assay device by detecting color changes thereto based on human perception is also disclosed. The method includes the steps of placing the assay device in optical proximity to an assay reader, such as described previously, such that the detection zone of the assay device is viewable by the at least one camera of the assay reader. The method further includes the step of generating an output signal by the at least one camera, which output signal is representative of an image of the detection zone of the assay device and which is indicative of a colorimetric change in the detection zone of the assay device.

Then, in accordance with the method of the present invention, the output signal from the at least one camera is received by the signal processor of the assay reader. The method then includes the step of converting the output signal from the at least one camera by the signal processor into measured colorimetric data. The comparator circuit of the assay reader then compares the measured colorimetric data relating to the assay device read by the assay reader with the dataset of sample readings based on human visual perceptions of the colorimetric changes of the reference assay devices stored in the storage memory of the assay reader.

In further accordance with the method of the present invention, the comparator circuit generates a comparison signal in response to comparing the measured colorimetric data with the stored dataset. The comparison signal from the comparator circuit is received by the signal processor, and, in accordance with the method, the signal processor generates a determination signal in response to the received comparison signal indicative of the presence, absence or quantity of an analyte in the fluid sample tested by the assay device read by the assay reader.

These and other objects, features and advantages of the present invention will be apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

Reference should initially be had to <FIG> of the drawings. There, a SNAP® lateral flow assay device <NUM> is shown adjacent to the reader <NUM> for the device <NUM> constructed in accordance with the present invention. It should be realized, of course, that the reader <NUM> of the present invention disclosed herein is not limited to use solely with a SNAP® assay device <NUM>, and that the structure of the reader <NUM> and method disclosed herein may be used with many different types of lateral flow assay devices <NUM> on the market, including reversible (bi-directional) flow chromatographic binding assay devices, uni-directional lateral flow assay devices and lateral flow assay devices having colloidal gold particles.

As shown in <FIG> of the drawings, the reader <NUM> of the present invention includes a housing <NUM> which is preferably in the form of a rectangular parallelepiped having a sloping top surface <NUM> on which is situated a display <NUM> and a graphical user interface (GUI) <NUM> having switches or a keyboard <NUM> and indicators for inputing data and commands and for receiving information concerning the tests being performed on a lateral flow assay device <NUM>, such as the SNAP® device. The display <NUM> is preferably a liquid crystal display (LCD), which effectively provides an indication of what is displayed in the read area <NUM> of the assay device <NUM>, including a display of the detection zones <NUM>, <NUM>, <NUM>, <NUM> and the control portion <NUM> of the read area <NUM>. The display <NUM> effectively recreates what is shown on the read area <NUM> of the lateral flow assay device <NUM> being tested, which is viewed by the camera <NUM> of the reader <NUM> in optical communication with the read area <NUM> of the assay device <NUM>. The housing <NUM> includes an opening or a port <NUM> on one side thereof to closely receive a lateral flow assay device <NUM>, such as the SNAP® device. When received by the port <NUM>, the lateral flow assay device <NUM> is maintained in a position such that the camera <NUM> of the reader <NUM> is in optical alignment with the detection zones <NUM>, <NUM>, <NUM>, <NUM> of the read area <NUM> on the assay device <NUM>.

Another form of the lateral flow assay device reader <NUM> of the present invention is shown in <FIG>. These figures show a simplistic view of the assay reader <NUM>, with the outer housing removed therefrom, to facilitate an understanding of some of the major components of the reader <NUM>.

More specifically, and referring to <FIG> of the drawings, it can be seen that the lateral flow assay device reader <NUM> of the present invention is, like the reader <NUM> shown in <FIG>, formed generally in the shape of a rectangular parallelepiped. The reader <NUM> has an internal frame <NUM> having sidewalls <NUM>, and a graphical user interface (GUI) <NUM> is preferably mounted on one of the sidewalls of the frame, such as the front sidewall <NUM>. The GUI <NUM> is preferably sloped with respect to the sidewall <NUM> of the frame <NUM> on which it is mounted so that a display <NUM> of the GUI <NUM> and any switches or keyboard <NUM>, or other indicators, may be easily viewed and accessed by a user of the assay reader <NUM>.

As can be seen from <FIG> of the drawings, one of the sidewalls <NUM> of the frame <NUM>, such as a lateral sidewall <NUM>, includes a cutout to form a pocket <NUM> having a ledge or support surface <NUM> on which a lateral flow assay device <NUM> may rest. This pocket <NUM> formed in the frame <NUM> is in alignment with an opening formed in the outer housing (not shown) of the reader <NUM> so that a user may have access to the pocket <NUM> and place an assay device <NUM> within the confines of the pocket <NUM>. The assay device <NUM>, when placed on the support surface <NUM> within the pocket <NUM>, is maintained in a position such that the read area <NUM> or window of the assay device <NUM> is in optical alignment with an optics module <NUM>, preferably a camera <NUM>, situated above it and mounted on the underside of a printed circuit board <NUM> affixed to the frame <NUM>. Preferably, the lateral flow assay device <NUM> includes calibration targets <NUM> in the form of markings or indicia which are placed in four corners surrounding the read window or area <NUM> of the lateral flow assay device <NUM>. The calibration targets <NUM> are used to insure that the read window or area <NUM> of the lateral flow assay device <NUM> placed within the pocket <NUM> of the reader <NUM> is in proper optical alignment with the optics module <NUM> of the reader <NUM>. Preferably, the lateral flow assay device <NUM> further includes a bar code <NUM> or other indicia to identify the type of assay device <NUM> placed in the reader <NUM>, such as the SNAP® 4Dx® Plus assay device, the SNAP® Heartworm RT assay device, the SNAP® Feline Triple® assay device, the SNAP® FIV/FeLV Combo assay device, the SNAP® Parvo assay device, the SNAP® Giardia assay device, the SNAP® Lepto assay device, the SNAP® ePL™ assay device, the SNAP® fPL™ assay device and the SNAP® Feline proBNP assay device, each of which is manufactured or distributed by IDEXX Laboratories, Inc. Clearly, other lateral flow device manufacturers can incorporate bar codes on their respective devices for proper identification.

The printed circuit board <NUM> referred to herein generally includes the circuitry that comprises the signal processing unit <NUM> of the reader <NUM>. The signal processing unit <NUM> includes a central processing unit (CPU) <NUM>, which carries out the operation of the reader <NUM> and its various functions, and various memories, including a random access memory (RAM) <NUM> and a read only memory (ROM) <NUM>, as will be explained in greater detail. Some operational software is embedded in the RAM <NUM> and test data is also stored therein, and the ROM <NUM> includes a database or dataset of sample readings of reference assay devices similar in structure and function to that of the assay device <NUM> read by the assay reader <NUM>. The sample readings are based on human visual perceptions of colorimetric changes in the detection zones of the reference assay devices.

The internal cavity, or pocket <NUM>, of the frame <NUM> of the assay reader <NUM> may include one or more diffuse reflectors <NUM> mounted on the internal surfaces of the sidewalls <NUM> thereof to insure that any light illuminating the lateral flow assay device <NUM> and emitted by one or more light emitting devices, such as light emitting diodes (LEDs), or other structured lighting <NUM>, is directed onto the read window or area <NUM> of the lateral flow assay device <NUM> situated within the pocket <NUM> of the assay reader <NUM>. The LED lighting <NUM> is preferably mounted on the underside of the printed circuit board <NUM> to direct light downwardly onto the lateral flow assay device <NUM>. The optics module <NUM> is also mounted on the underside of the printed circuit board <NUM> and situated above the pocket <NUM> and a lateral flow assay device <NUM> received therein, and may include one or more cameras <NUM>, as mentioned previously.

As can be seen from <FIG> of the drawings, the assay reader <NUM> may include connectors or ports <NUM> for Ethernet or internet connections to external equipment. In the case of IDEXX Laboratories, Inc, this could include connection to the IDEXX VetLab® Station which is capable of communicating with other instruments, such as the VetTest™, Catalyst DX™, Catalyst One™ and SediVue Dx™ analyzers manufactured or distributed by IDEXX Laboratories, Inc. These connectors <NUM> are preferably mounted on a rear sidewall <NUM> of the frame <NUM>, or the outer housing, of the assay reader <NUM>. Furthermore, the assay reader <NUM> includes a speaker or transducer <NUM>, also mounted on the rear sidewall <NUM> or another sidewall <NUM> of either the outer housing or the internal frame <NUM> of the assay reader <NUM>, to convey audible information to the user of the assay reader <NUM>. The speaker, or transducer <NUM>, and the Ethernet and internet ports <NUM> are electrically connected to the signal processing unit <NUM> of the assay reader <NUM>.

<FIG> shows a block diagram of some of the electrical and optical components of the assay reader <NUM> of the present invention. As can be seen from <FIG>, the assay reader <NUM> preferably includes an optics module <NUM>, as mentioned previously. The optics module <NUM> preferably has at least one camera <NUM> that is positioned on the reader <NUM> to view the detection zones <NUM>, <NUM>, <NUM>, <NUM> (e.g., the "dots" mentioned earlier) in the read area <NUM> of the assay device <NUM> placed in optical proximity to the instrument. The at least one camera <NUM> generates an output signal which is representative of an image of the read area <NUM> and detection zones <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM> and which is indicative of a colorimetric change in the detection zones <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM>. Detection zones are not limited to "dots" but can include lines or other shapes where a capture reagent is disposed on the matrix upon which the sample flows.

As also mentioned previously, there is a signal processor <NUM> forming part of the assay reader <NUM>. This signal processor <NUM> is in electrical communication with the optics module <NUM>. The signal processor <NUM> receives the output signal from the at least one camera <NUM> and converts the signal into measured colorimetric data.

The assay reader <NUM> further includes a storage memory (such as the ROM <NUM> mentioned earlier) that is in electrical communication with the signal processor <NUM>. The storage memory <NUM> has stored therein a dataset of sample readings of reference assay devices that are similar in structure and function to that of the assay device <NUM> read by the instrument <NUM>. The sample readings are based on human visual perceptions of colorimetric changes in the detection zones of the reference assay devices.

The assay reader <NUM> further includes a comparator circuit <NUM> which is in electrical communication with the signal processor <NUM> and which may form part of the signal processor <NUM>. The comparator circuit <NUM> compares the measured colorimetric data relating to the assay device <NUM> read by the instrument <NUM> with the stored dataset or database of sample readings based on human visual perceptions of the colorimetric changes of the reference assay devices, and generates a comparison signal in response thereto. The signal processor <NUM> receives the comparison signal from the comparator circuit <NUM>, and in response thereto, generates a determination signal that is indicative of the presence, absence or quantity of an analyte (e.g., an antigen or an antibody) in the fluid sample tested by the assay device <NUM> read by the instrument <NUM>.

As mentioned previously, the optics module <NUM> may include at least one camera <NUM>. However, in an alternative embodiment of the present invention, the optics module <NUM> of the assay reader <NUM> may include at least one light source <NUM> and a light detector <NUM>. The light source <NUM> and light detector <NUM> may be formed, for example, as a reflectometer <NUM> or a fluorometer <NUM>. The at least one light source <NUM> emits light and is positioned on the assay reader <NUM>, such as on the underside of the overhead printed circuit board <NUM>, to direct the light onto the detection zones <NUM>, <NUM>, <NUM>, <NUM> of the read window <NUM> of the assay device <NUM> placed in optical proximity to the reader <NUM>. The light detector <NUM> receives reflected or fluoresced light emanating from the detection zones <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM> in response to the light directed thereon by the at least one light source <NUM>. The light detector <NUM> generates an output signal in response to the reflected or fluoresced light received by the light detector <NUM>. The output signal from the light detector <NUM> is indicative of a colorimetric change in the detection zones <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM>. This output signal is provided to the signal processor <NUM> of the assay reader <NUM>.

One of the important distinguishing features of the assay reader <NUM> of the present invention over other instruments used to read lateral flow assay devices <NUM> is that the assay reader <NUM> "mimics" what a human would do when perceiving whether there is a color change in the detection zone or zones <NUM>, <NUM>, <NUM>, <NUM> of the lateral flow assay device <NUM>. In other words, the assay reader <NUM> of the present invention bases the determination of whether there is a colorimetric change in the detection zone <NUM>, <NUM>, <NUM>, <NUM> of the lateral flow assay device <NUM> that is indicative of the presence, absence or quantity of an analyte in the fluid sample tested by the assay device <NUM> and read by the assay reader <NUM> based on human visual perception, and not based on an algorithmic rule which makes such determinations in conventional lateral flow assay device readers. The dataset or database of sample readings of reference assay devices of similar function and structure to that of the assay device <NUM> read by the assay reader <NUM> is, basically, a library of human visual calls (i.e., determinations) to images from which their observations were made. More specifically, in a specific embodiment, this stored library of human visual observations preferably includes about <NUM> million, or more, sample readings, or observations, made by humans of similar lateral flow assay devices. For example, if a number of manual or human reads of images of lateral flow assay devices in the dataset stored in the memory <NUM> reflect a positive, or negative, determination of crescent-shaped blue detection dots, or speckles instead of a full circular dot, or a light colored detection dot, then the comparator circuit <NUM> of the assay reader <NUM>, and the signal processor <NUM> in electrical communication therewith, will make a similar determination, based on the stored dataset of sample readings of human visual perceptions of the colorimetric changes of the reference assay devices. From this, the assay reader <NUM> of the present invention, and in particular, the signal processor <NUM> thereof, generates a determination signal that is indicative of the presence or quantity, or absence, of an analyte in the fluid sample tested by the assay device <NUM> read by the assay reader <NUM>.

As further mentioned previously, a method for reading a lateral flow assay device <NUM> by detecting color changes thereto based on human perception is also disclosed herein. The method is performed by a lateral flow assay reader <NUM>, which preferably has an optics module <NUM>, a signal processor <NUM> in electrical communication with the optics module <NUM>, a storage memory <NUM> in electrical communication with the signal processor <NUM> and a comparator circuit <NUM> in electrical communication with the signal processor <NUM>. The optics module <NUM> has at least one camera <NUM>. The storage memory <NUM> has stored therein a dataset of sample readings of reference assay devices similar in structure and function to that of the assay device <NUM> read by the assay reader <NUM>. The sample readings of the dataset are based on human visual perceptions of colorimetric changes in the detection zones of the reference assay devices.

The method includes the step of placing the lateral flow assay device <NUM> in optical proximity to the assay reader <NUM> such that the detection zone <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM> is viewable by the at least one camera <NUM> of the assay reader <NUM>. Then, the method includes the step of generating an output signal by the at least one camera <NUM> which is representative of an image of the detection zone <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM> and which is indicative of a colorimetric change in the detection zone <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM>. The method further includes the steps of receiving by the signal processor <NUM> of the assay reader <NUM> the output signal from the at least one camera <NUM>, and converting by the signal processor <NUM> the output signal from the at least one camera <NUM> into measured colorimetric data. This measured colorimetric data is preferably stored in the RAM <NUM>.

The method of the present invention further compares, using the comparator circuit <NUM> of the assay reader <NUM>, the measured colorimetric data relating to the assay device <NUM> read by the assay reader <NUM> with the dataset of sample readings based on human visual perceptions of the colorimetric changes of the reference assay devices stored in the storage memory <NUM> of the assay device reader <NUM>. Then, the method includes the steps of generating by the comparator circuit <NUM> a comparison signal in response to comparing the measured colorimetric data with the stored dataset, receiving by the signal processor <NUM> the comparison signal from the comparator circuit <NUM>, and generating by the signal processor <NUM> a determination signal in response to the received comparison signal indicative of the presence, absence or quantity of an analyte in the fluid sample tested by the assay device <NUM> read by the assay reader <NUM>.

The at least one camera <NUM> of the assay reader <NUM> may be a charge-coupled device (CCD). However, and as mentioned previously, the optics module <NUM> may use at least one light source <NUM>, and a light detector <NUM> instead of the camera <NUM>. Then, the method of the present invention would include the steps of directing light from the at least one light source <NUM> of the optics module <NUM> of the assay reader <NUM> onto the detection zone <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM>, receiving by the light detector <NUM> of the optics module <NUM> of the assay reader <NUM> reflected or fluoresced light emanating from the detection zone <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM> in response to the light directed thereon by the at least one light source <NUM>, and generating by the light detector <NUM> an output signal in response to the received reflected or fluoresced light, the output signal being indicative of a colorimetric change in the detection zone <NUM>, <NUM>, <NUM>, <NUM> of the assay device <NUM>. This output signal from the light detector <NUM> is provided to the signal processor <NUM> of the assay reader <NUM> and is converted by the signal processor <NUM> into measured colorimetric data.

Claim 1:
A method for determining the presence, absence, or quantity of an analyte in a fluid sample tested by an assay device (<NUM>), the method comprising:
comparing measured colorimetric data relating to an assay device (<NUM>) with a dataset of sample readings based on human visual perceptions of colorimetric changes of reference assay devices, the dataset of sample readings stored in a storage memory (<NUM>) of an assay reader (<NUM>);
generating a comparison signal in response to the comparing the measured colorimetric data with the dataset of sample readings; and
generating a determination signal in response to the comparison signal, the determination signal indicative of the presence, absence, or quantity of an analyte in a fluid sample tested by the assay device (<NUM>) read by the assay reader (<NUM>).