The value of monitoring human papillomavirus DNA results for Papanicolaou tests diagnosed as atypical squamous cells of undetermined significance: a College of American Pathologists Q-Probes study of 68 institutions.

Abstract

Papanicolaou (Pap) tests are often diagnosed as atypical squamous cells of undetermined significance (ASC-US). Human papillomavirus (HPV) DNA testing has been proposed as a quality metric for this diagnosis. To measure the frequency of HPV positivity in Pap tests diagnosed as ASC-US and to examine laboratory variables that are associated with institutional deviation from the mean percent of HPV positivity. As part of a College of American Pathologist Q-Probes program, 68 participating laboratories retrospectively identified approximately 50 consecutive ASC-US Pap tests that had HPV testing results. The mean percentage of HPV positivity for ASC-US was 43.74% among institutions surveyed, but it had a broad distribution, with an SD of 17.77%. Associations were found for lower difference of the institutional mean from the surveyed interinstitutional mean percentage of positive HPV with (1) higher numbers of Pap tests in the past year that had HPV testing, (2) in-house HPV testing, and (3) teaching hospitals. All 3 factors correlated with a larger volume of Pap tests per institution. An association was found between patient age and the probability of a positive HPV result, indicating a dependence upon prevalence of HPV. Larger volumes of Pap tests may offer an opportunity to gain greater comfort in interpreting Pap tests. While there is significant variability in interinstitutional HPV-positive rates in ASC-US Pap tests, monitoring the HPV-positive rate in ASC-US Pap tests is a valuable broad measure of quality. Performance beyond 2 SDs of the mean should prompt reassessment of diagnostic criteria used in the evaluation of Pap tests and/or investigation of the prevalence of HPV positivity in the population from which the Pap tests are obtained.