Non-16/non-18 high-risk human papillomavirus types predominate in anal cytology categories of negative for intraepithelial lesion and atypical cells of undetermined significance

IntroductionScreening for anal carcinoma continues to grow despite controversy regarding its efficacy. High-risk human papillomavirus (HR-HPV) has been adopted as a cotest with anal Papanicolaou tests. We sought to identify the prevalence of HR-HPV types in the most common anal cytology specimens: negative for intraepithelial lesion or malignancy (NILM) and atypical squamous cell of undetermined significance (ASC-US).Materials and methodsAnal cytology specimens were identified and tested for HR-HPV using Roche cobas 4800 HR-HPV analysis (Roche Molecular Systems, Inc., Indianapolis, Ind) and, if positive, typed further for: HPV-16, -18, and/or non-16/non-18 “other” HR-HPV type.ResultsThere were 642 specimens from 538 patients. The most common interpretation was NILM (48.6%) and ASC-US (25.7%). Of NILM cases, 47% were HR-HPV+ (53% in men, 33% in women, P = 0.03, χ2). In ASC-US cases, 73% were HR-HPV+ (74% in male patients, 70% in female patients). The most common HPV subtype was non-16/non-18 HR-HPV “other” types in 89% of cases. HPV-16 and HPV-18 were positive in 35% and 18% of cases, respectively. In patients with non-16/non-18 HR-HPV+ anal cytology, 16 of 79 had biopsies histologically diagnosed as at least high-grade squamous intraepithelial lesion (HSIL+). However, the relative risk of having HSIL+ was 2.3-times higher for anal cytology positive for HPV-16, -18, with/without coinfection with non-16/non-18 HR-HPV than those positive for non-16/non-18 “other” HR-HPV types alone.ConclusionsNon-16/non-18 “other” HR-HPV types are most prevalent in anal cytology interpretations of NILM and ASC-US. Patients with HR-HPV+ NILM or ASC-US, negative for HPV-16/-18, are at lower relative risk of having subsequent histologic HSIL+, but a percentage of these patients still harbor HSIL+ on biopsy.