Human papillomavirus (HPV) is one of the most commonly sexually transmitted infectious pathogens causing cervical cancer in women. Testing for HPV infection is a standard of care as a reflex for ASCUS cytology results in women 21 and older and as a primary adjunctive screen with a Pap test in women 30 to 65 years of age. Genotyping for HPV 16 and 18 genotypes has become a decision making for colposcopy for patients with normal cytology.
The purpose of this study was to determine the HPV18 positivity rate of the APTIMA® HPV 16 18/45 Genotype Assay by testing specimens which are known to be HPV18 positive by cobas® 4800 HPV assay in patients with negative for intraepithelial lesion or malignancy (NILM) population. Patient with abnormal Pap results were also included in this study. An additional purpose was to evaluate agreement between the Aptima and the Aptima GT Assays in patients known to be HPV18 positive.
A total of 279 de-identified residual PreservCyt specimens with previous HPV 18 positive results by the cobas test were tested with the Aptima GT Assay. Additionally, 245 of these samples were also tested with the Aptima assay. These specimens included cases with normal and abnormal cytology findings.
The following discrepancies were found between the two assays: 10 cases that were Aptima 18/45 positive were negative for pooled Aptima HPV. 79 cases were HPV 18 positive on cobas but HPV 18/45 negative on Aptima; 32 of these had abnormal cytology and 47 had normal cytology. The agreement between the two assays for cases with normal and abnormal cytology was 65.9% and 77.3% respectively, giving an overall agreement of 71.7%. In comparison to Roche, Aptima had a false negative rate of 17.9%, evenly distributed between cases with normal and abnormal cytology.
Of 279 cases that were HPV 18 positive by cobas, the Aptima GT Assay detected 200. Discrepancies were present in 32 cases with abnormal and 47 with normal cytology. Among concordant cases (those detected by both cobas and the Aptima GT Assay, there were 10 cases were not detected by the first-line Aptima assay. These cases would not typically be tested with the Aptima GT Assay because the first-line Aptima assay results. This can have significant consequences in patient diagnosis and management.