Quantitative laser-scanning lateral flow immunoassay of luteinizing hormone with a handheld analyzer

Abstract

Lateral flow immunoassay (LFIA) is a promising analytical tool for the rapid and sensitive diagnostics of health conditions and diseases. However, conventional LFIA generally provides only qualitative and semi-quantitative results. This report introduces a novel technique known as laser-scanning LFIA, along with a prototype handheld analyzer known as the quantitative mobile immunoanalyzer (QMIA), to enhance its quantitative capability and practicality. The method employs a stepper motor to move a green laser beam across the test strip, while two photodiodes detect the light scattered from the nitrocellulose membrane. By using control line intensities as internal standards, we validated the assays with luteinizing hormone (LH) test strips, which have a cut-off value of 25 mIU/mL. The validation demonstrated less than 20% variability at LH concentrations above 1 mIU/mL. The utility of the assays was further showcased through daily monitoring of urinary LH levels in male and female volunteers over the course of a month. The QMIA reader is compact, reliable, and user-friendly, offering distinct advantages over existing devices for at-home and point-of-care testing.