Abstract
Background The Hybrid Capture 2 (HC2) High-Risk HPV DNA assay serves as a triage test in the Slovenian national cervical cancer screening programme ZORA. To improve the limited analytical accuracy of HC2 test results near the cut-off value (1.0 relative light units/cut-off (RLU/CO)), we follow an internal protocol of repeating the test on all samples with borderline results within the 0.7-2.0 RLU/CO interval. The aim of the study was (i) to determine the clinical relevance of HC2 test results within three different "grey zones" for samples stored in Specimen Transport Medium (STM) and (ii) to determine whether the current algorithm of retesting "grey zone" STM specimens with the HC2 assay is clinically relevant. Patients and methods The study included 594 women between 20 and 65 years of age. All participating women were referred for colposcopy, and in cases of abnormal results, biopsy was performed. We assessed the distribution of HC2 test results and the corresponding proportion of cervical intraepithelial neoplasia grade 2 or worse (CIN2+) lesions in three different "grey zones" (1.0-2.5, 0.4-4.0 and 0.7-2.0 RLU/CO), retested specimens with results within a 0.4-4.0 RLU/CO interval and calculated the sensitivity and specificity for HC2 at different RLU/CO values. Results The proportion of specimens within 1.0-2.5, 0.4-4.0 and 0.7-2.0 RLU/CO intervals was 3.9%, 10.8% and 4.5%, respectively. The proportion of CIN2+ lesions within these "grey zones" was 2.5%, 5.6% and 1.2%, respectively. Retesting the samples did not detect any additional CIN2+ cases. Within the 1.0-2.5 RLU/CO interval, the sensitivity decreased from 93.8% to 91.4%, while the specificity increased from 63.3% to 67.5%; for the 0.4-4.0 RLU/CO interval, the sensitivity decreased from 95.1% to 89.5%, while the specificity increased from 56.8% to 69.4%; and for the 0.7-2.0 RLU/CO interval, the sensitivity remained nearly constant (94.4 vs. 93.2%), while the specificity increased from 60.6% to 66.4%. Conclusions Our results show that retesting STM samples within the "grey zones" is not necessary. Retesting samples in the negative "grey zone" does not increase sensitivity, and retesting in the positive "grey zone" is not followed by a less intensive management of women, since these women are recalled regardless of the results of the retest. Furthermore, the majority of samples retain the original HC2 results after retest, and the number of CIN2+ lesions among women with "grey zone" HC2 results is low.