The importance of first-void urine for assessing HPV-specific antibodies: A comparison with midstream urine.

Humoral immunity to HPV is typically assessed via serum, which reflects systemic immune responses. However, local sampling may offer a more accurate representation of immunity at the site of infection. First-void urine (FVU), a self-collectible cervicovaginal sample, presents a non-invasive alternative. The difference in HPV-specific IgG concentrations between FVU and the subsequent midstream urine fraction, however, has not yet been systematically evaluated. In this proof-of-concept study, we examined the HPV16-specific IgG concentrations in paired FVU and midstream urine (MSU) samples collected from 19 healthy female volunteers using two FVU collection devices (10 mL and 20 mL). Antibody detection rates were significantly higher in FVU (89-95% for 10 and 20 mL devices, respectively) compared to MSU (53-58% for MSU collected after the 10 and 20 mL FVU collection, respectively), with no significant difference between the two FVU volumes. These findings highlight the critical importance of capturing the initial urine stream, for optimal detection of female genital tract-derived antibodies in urine.