Disclosed is an assay device to determine the presence of at least one analyte of interest in a liquid sample, the device comprising means for generating a first signal (the ‘test’ signal) which indicates the presence and/or amount of analyte of interest in the sample; and means for generating a second signal, the generation of which second signal indicates both (a) the test has been successfully conducted, and that (b) sufficient time has elapsed following contact of the assay device with the liquid sample for the test to be read and the first signal to have been properly generated.
1. An assay device to determine the presence of at least one analyte of interest in a liquid sample, the device comprising a test strip on which is deposited:
a first latex-labeled analyte-specific binding reagent for generating a first signal, or ‘test’ signal, which indicates the presence and/or amount of analyte of interest in the sample; and
a second latex-labeled specific binding reagent from a control latex suspension having a latex concentration of at least 1.5% w/v for generating a second signal, the generation of which second signal indicates both
(a) the test has been successfully conducted, and that
(b) sufficient time has elapsed following contact of the assay device with the liquid sample for the test to be read and the first signal to have been properly generated.
2. The device of claim 1 , wherein the analyte of interest is hCG.
3. The device of claim 1 , wherein the device is a lateral flow immunochromatographic assay device.
4. The device of claim 1 , wherein the second signal has a signal development time of about 1 minute.
5. The device of claim 1 , wherein the second signal is a visible signal which appears in a portion of the test device covered by a layer of translucent material.
6. The device of claim 1 , wherein the second signal has a signal development time of less than 10 seconds.
7. The device of claim 6 , wherein the second signal has a signal development time of less than 8 seconds.
8. A method of performing an assay to determine the presence of an analyte of interest in a sample, the method comprising the steps of: contacting an assay device according to claim 1 with the sample; observing the appearance of the second signal; observing the appearance of the first signal when the second signal has appeared; and concluding that the analyte of interest is present in the sample if the first signal appears when the second signal has appeared.
9. The method of claim 8 , wherein the sample is a sample of body fluid.
10. The method of claim 9 , wherein the sample is urine.
11. The method of claim 8 , wherein the analyte of interest is hCG.
12. The device of claim 1 , wherein the sufficient time is a pre-determined time.
13. The device of claim 1 , wherein the second latex-labeled specific binding reagent is deposited on the test strip at a position more than 16.5 mm measured from a position at which the liquid sample is to be applied to the test strip.
14. The device of claim 13 , wherein the second latex-labeled specific binding reagent is deposited on the test strip at a position less than or equal to 25 mm measured from a position at which the liquid sample is to be applied to the test strip.
15. The device of claim 1 , wherein the second latex-labeled specific binding reagent is deposited on the test strip at a position less than or equal to 25 mm measured from a position at which the liquid sample is to be contacted to the test strip.
16. The device of claim 1 , further comprising a laminate placed over the deposit of second latex-labeled specific binding reagent.
17. The device of claim 16 , wherein the laminate comprises a translucent laminate.
18. The device of claim 1 , wherein the device comprises up to about 22 micrograms of second latex-labeled specific binding reagent.
19. The device of claim 1 , wherein the first latex-labeled analyte-specific binding reagent comprises a first antibody specific for the at least one analyte of interest.
20. The device of claim 19 , wherein the second latex-labeled specific binding reagent comprises a second antibody specific for a third antibody that is specific for the at least one analyte of interest.
21. The device of claim 1 , wherein the test strip has a capillary flow time of about 180 seconds per 4 centimeters.
22. A method of making the device of claim 1 , comprising:
depositing the first latex-labeled analyte-specific binding reagent on the test strip; and
depositing the second latex-labeled specific binding reagent on the test strip from a control latex suspension having a latex concentration in the range of about 1.5% to 2% w/v.