Sensitivity and colour intensity enhancement in lateral flow immunoassay tests by adjustment of test line position.

In this article, we have enhanced the sensitivity and limit of detection of lateral flow immunoassay tests, exemplified for the detection of human chorionic gonadotropin (pregnancy) through determination of proper test line position. Test line position affects the flow velocity and concentration profile of analytes at the test line, which itself impacts the reaction rate and thus the colour intensity. The flow velocity was precisely modelled, both analytically and numerically, and the predicted analytes' moving front (lateral) velocity was experimentally verified. Evolution of the velocity magnitude was determined to locate points with proper capillary velocity and accumulated bed-volume. This provides insights into the essence of LFIAs performance for simple and easy to practice improvements. The colour intensity was measured by quantifying the RGB of the resulting test line colours. The response colour intensity was enhanced for at least 20%, up to 40% by proper displacement of the test line position, and the limit of detection was cut by half to 10 IU/L.