Adjunctive p16 Immunohistochemistry Use in Cervical Biopsies According to LAST Criteria

The Lower Anogenital Squamous Terminology (LAST) Project recommends the use of p16 immunohistochemistry as an adjunct to morphologic assessment of cervical biopsies according to a specific set of criteria. We analyzed the effect of adjunctive p16 according to LAST criteria in a US-based diagnostic utility study involving 70 surgical pathologists providing a total of 38,500 reads on cervical biopsies. Compared with the results obtained using hematoxylin and eosin-stained slides only, including p16-stained slides per LAST criteria increased sensitivity and specificity for diagnosing histologic high-grade squamous intraepithelial lesions across all cases by 8.1% (95% confidence interval [95% CI], 6.5-9.7; P< 0.0001) and 3.5% (95% CI, 2.8-4.2; P< 0.0001), respectively, using expert consensus diagnoses on hematoxylin and eosin+p16 as reference. Within the subset of cases classified by the pathologists as fulfilling the LAST criteria, adding p16 significantly increased both sensitivity (+11.8%; 95% CI, 9.5-14.0; P< 0.0001) and specificity (+9.7%; 95% CI, 7.8-11.5; P< 0.0001). However, a comparable improvement in sensitivity (+11.0%; 95% CI, 7.8-14.1; P< 0.0001) was found when p16 was used in cases for which p16 staining was not ordered per LAST by the pathologists, whereas specificity decreased by −0.8% (95% CI, −1.1 to −0.5; P< 0.0001). The study demonstrates a clinically and statistically significant increase in sensitivity and specificity for high-grade squamous intraepithelial lesion when p16 is used according to LAST criteria. Expanding the use of p16 into nonLAST cases would lead to a comparable improvement in sensitivity within this subgroup of biopsies, at the cost of a minimal, but statistically significant difference in specificity.