Smartphone-based urine colourimetric assay for home self-screening of HPV infection

Currently, producing NPSH after HPV infection of cells has been confirmed. These NPSH-containing substances accumulate around the urethral opening and are subsequently washed out with urine. Therefore, indirect detection of HPV infection by assessing NPSH levels in urine is feasible, but it has not been reported in detail so far. Here, an assay using phosphotungstic acid to oxidise and produce colour changes by NPSH in urine was developed. This assay enabled the rapid, non-invasive identification of HPV infection by detecting the metabolic byproduct NPSH produced by HPV-infected cells. Employing a smartphone-based device, developed using an ambient light sensor, reduces the cost and simplifies the operation associated with the colourimetric assay. The colourimetric assay was used to detect L-cysteine and L-ascorbic acid standard substance (as NPSH mimics), the limited of detection were 0.12 mM and 31.25 μM, respectively, with high reproducibility and stability. When this colourimetric assay was used to evaluate urine samples from individuals suspected of HPV infection, along with other at-home self-screening methods for HPV nucleic acid detection in urine, showed comparable sensitivity and specificity. Compared with nucleic acid detection in urine, this colourimetric assay is cost-effective, user-friendly, amenable to self-sampling, and enables testing at one's convenience and location of choice, which is more suitable for home self-testing or population self-screening.