Development and validation of a wart-associated human papilloma virus genotyping assay for detection of HPV in cutaneous warts.

Abstract

Cutaneous warts are infectious disorders caused by human papillomavirus (HPV). A recent study revealed that the HPV genotype influences the natural course and response to treatment for plantar warts, suggesting that HPV genotyping could potentially be used to optimize wart treatment schemes. For this purpose, a wart-associated HPV genotyping assay was developed. The assay was subjected to an intensive validation process including, i.a., empiric determination of the annealing temperature, primer-probe optimization, evaluation of the analytical specificity and sensitivity, viral load quantification, and qualitative as well as quantitative analysis of intra-run repeatability and inter-run reproducibility. The newly developed assay was employed in a small-scale HPV genotyping study of wart biopsies (n = 50). The assay exhibited an analytical type-specific sensitivity and specificity of 100% (95% confidence interval [CI]: 83.9%-100%). The limit of quantification of the tested sequences corresponded to less than 17 viral copies/µl, while the limit of detection was less than 5 copies/µl. Very good to excellent agreements were gained between intra- and inter-run measurements (κ = 0.85-1.00) and coefficients of variation of the quantitative agreements were less then 3%. 22.5% (95% CI: 11%-39%) of the analyzed biopsies were negative for the tested HPV types, while 35% (95% CI: 21%-52%) contained multiple infections. The wart-associated HPV quantitative polymerase chain reaction assay was proven to be highly sensitive and specific. Multiple HPV infections were detected in 35% of lesions, contradicting the current literature claiming that in immunocompetent patients only 4%-16% of warts exhibit multiple HPV infections. This assay is qualified to be implemented in development of future genotype specific wart treatment strategies.