Interactive test system and method for detecting an analyte
A system comprised of an apparatus and a test device is described. The test device and the apparatus are designed to interact to determine the presence or absence of an analyte of interest in a sample placed on the test device. The test device and apparatus interact to provide a timer feature for determining a test device specific adjustable cut-off value that is used to ascertain whether signal from a test line in the device corresponds to a positive or negative results, irrespective of the time elapsed since placement of sample on the test device. The adjustable cut-off value renders the system relatively insensitive to incubation time of the test device, where if the incubation time is shorter or longer than needed for accuracy of a test result, the analyzer will report an invalid result, thus preventing the reporting of an incorrect (false negative or false positive) result.
1 . A system, comprising:
a test device comprising:
(a) a label zone comprising
(i) a first population of mobilizable, detectable particles for specific binding to a test analyte in a sample; and
(ii) a second population of mobilizable, detectable particles for specific binding to a non-test analyte but not to the test analyte;
(b) a first detection site at a first position comprising a first binding member having specific binding affinity for detectable particles in the first population bound to the test analyte; and
(c) a second detection site at a second position that is separate from the first position, the second detection site comprising a second binding member having specific binding affinity for detectable particles in the second population bound to the non-test analyte; and
an analyzer comprising:
(1) an opening dimensioned to receive the test device,
(2) an optical system for detection of a signal generated from the first population of mobilizable, detectable particles at the first position and the second population of mobilizable, detectable particles at the second position when each population reaches a specific and separate position on the test device,
(3) a processor communicatively coupled with the optical system to receive the signal and to evaluate a ratio of a signal detected from all or a portion of the first population of mobilizable, detectable particles to a cut-off value to determine a presence or an absence of analyte in the sample based on the ratio, and
(4) a memory storing the cut-off value, wherein the cut-off value is an exponentially transformed signal from all or a portion of the second population of mobilizable, detectable particles, adjusted by an empirically determined constant value for a manufacturing lot comprising the test device.
2 . The system of claim 1 , wherein the signal from all or a portion of the first population of mobilizable, detectable particles is used by the processor to provide a quantitative or semi-quantitative amount of analyte present in the sample.
3 . The system of claim 1 , wherein signal from the second population of mobilizable, detectable particles is mathematically transformed by the processor in the analyzer to provide a transformed signal.
4 . The system of claim 3 , wherein the signal from the second population of mobilizable, detectable particles is mathematically transformed by the processor using an exponential transformation.
5 . The system of claim 4 , wherein the exponential transformation is selected from an exponential value of between 1.3-1.8.
6 . The system of claim 5 , wherein transformed signal is multiplied by a constant value specific for an analyte to yield a transformed cut-off value.
7 . The system of claim 6 , wherein the constant value is determined for each specific manufacturing lot of analyte.
8 . The system of claim 1 , wherein the test device is a lateral flow immunoassay.
9 . The system of claim 8 , wherein one or both of the first population of mobilizable, detectable particles and the second population of mobilizable, detectable particles is comprised of particles comprised of a fluorescing lanthanide compound.
10 . The system of claim 9 , wherein the fluorescing lanthanide compound is europium.
11 . A method for determining presence or absence of an analyte in a sample, comprising:
depositing a sample on a test device comprising a first population of detectable particles for detection of an analyte in a sample and a second population of detectable particles for specific binding to a non-test analyte,
inserting the test device into an analyzer capable of receiving the test device, the analyzer comprising an optical system for detection of a signal generated from each of the first and second populations of particles when each population reaches a specific position on the test device,
detecting an intensity of signal from all or a portion of the second population of particles;
calculating a cut-off value used in an algorithm in the analyzer to determine whether the signal from all or a portion of the first population of particles corresponds to the presence or absence of analyte in the sample, wherein said calculating comprises calculating a transformed cut-off value by exponentiation of the signal from all or a portion of the second population of particles, and comparing the transformed cut-off value by signal from all or a portion of the first population of particles; and
reporting a result from the calculating.
12 . The method of claim 11 , wherein the analyte of interest is a protein.
13 . The method of claim 12 , wherein the protein in human chorionic gonadotropin.
14 . The method of claim 12 , wherein the analyte of interest is an infectious analyte.
15 . The method of claim 14 , wherein the infectious analyte is a virus or a bacteria.
16 . The method of claim 15 , wherein the infectious analyte is influenza A or influenza B.
17 . The method of claim 11 , wherein the exponent in the exponentiation is between 1.2-1.8.