Resolution of Equivocal Results With the Hybrid Capture II High-risk HPV DNA Test: A Cytologic/Histologic Review of 191 Cases

Abstract

The Hybrid Capture II (HC II, Digene) high-risk human papilloma virus (HPV) (hrHPV) DNA test is an in vitro nucleic acid hybridization assay that uses enhanced chemiluminescence for the qualitative and semiquantitative detection of hrHPV in cervical samples. Patient samples are concomitantly tested with positive and negative DNA controls and results reported as positive or negative on the basis of a ratio of relative light units to a cutoff value derived from the positive control (RLU/CO). Samples with a ratio <1.0 RLU/CO are expressed as negative for hrHPV, samples with a ratio >2.5 RLU/CO are expressed as positive for hrHPV, and samples with a ratio between these numbers are submitted for retesting. These "equivocal" values are resulted as positive for hrHPV if either of 2 subsequent test values equals or exceeds 1.0 RLU/CO. Samples that show <1.0 RLU/CO after 2 repeat tests are resulted as negative for hrHPV. In this study, we evaluated all hrHPV test results over a 17-month period in our institution. Initial tests showing an equivocal result were analyzed for final retesting result, and for all corresponding and subsequent cytology and histology results. All hrHPV tests were conducted on SurePath (TriPath) or ThinPrep (Cytyc) cervical cytology specimens using the HC II hrHPV DNA test. Subsequent hrHPV tests also were correlated with incident and follow-up findings. A total of 4792 hrHPV test results were evaluated. Of these, 191 (4%) showed equivocal initial results. When retested, 178 of the 191 samples (93%) resulted positive for hrHPV on first retest and an additional 8 resulted positive for hrHPV on the second retest, bringing the total positive tests to 186 out of 191 (97.4%). Five samples (2.6%) out of 191 were finally expressed as negative for hrHPV. Corresponding cytologic interpretations for the 191 specimens were as follows: NILM-30, atypical squamous cell of undetermined significance (ASC-US)-138, atypical squamous cells--cannot exclude HSIL-13 (ASC-H-13), LSIL-9, and high-grade squamous intraepithelial lesion (HSIL)-1. Follow-up histology was available for 60 of the 191 equivocal cases and showed cervical intraepithelial neoplasia (CIN) II or CIN III in 7 cases, CIN I in 13 cases, and negative or reactive changes in 40 cases. On the basis of the results, repeat testing of equivocal specimens might not be necessary as these specimens are overwhelmingly found to be positive for hrHPV. Additionally, hrHPV tests falling in the equivocal range should be considered as definite positive tests, as follow-up results in this cohort demonstrate that significant histologic abnormalities are associated with 10.5% of these cases (20/191), and with 33% of those biopsied (20/60) cases.