A Comparison of E6H4 and G175-405 p16-specific Monoclonal Antibodies in Oropharyngeal Squamous Cell Carcinoma.

The purpose of this investigation is to directly compare G175-405 and E6H4 p16-specific antibodies as immunomarkers of HPV-driven oropharyngeal carcinoma. The investigators designed a retrospective analysis using specimens from an archived tissue bank with known in situ hybridization and polymerase chain reaction status for HPV DNA. Fifty randomly selected oropharyngeal specimens were evaluated with both the G175-405 and E6H4 p16-specific monoclonal antibodies. Two pathologists, blinded to the HPV-specific testing status, evaluated p16 positivity for both antibody clones. Interrater agreement was determined using a Cohen κ coefficient. Sensitivity and specificity values were calculated using a standard 2×2 contingency table, then compared using McNemar test. Interrater agreement for interpretation of p16 expression was 92% (κ=0.84) for the G175-405 clone and 100% for the E6H4 clone (κ=1.0). The G175-405 stain had a sensitivity of 0.917 and specificity of 0.846. The E6H4 stain had a sensitivity of 1.000 and specificity of 0.769. Using McNemar test, there were no significant differences found for sensitivity (P=0.480) or specificity (P=0.480) values. The results of this study suggest that though both G175-405 and E6H4 antibody stains are statistically comparable immunomarkers for HPV-driven oropharyngeal carcinoma, the E6H4 clone offers improved interobserver reliability.