We have developed a low-costportable reader for thermometric lateral flow immunoassay (TLFIA) using colloidal goldlatex beads as reportersa continuous-wave green laser as the heating source. Instead of using infrared cameras, a single-element infrared sensor is employed for temperature sensing without compromising the sensitivity of the reader. The thermometric assay provides a 10× higher sensitivity than color visualizationthe results are sufficiently quantitative to support decision making in point-of-care testing for infectious diseases (such as COVID-19).