Evaluation of Cycle Threshold (Ct) Values for Detecting High-Risk HPV in Self-Collected Vaginal Samples as a Triage...

Background/Objectives: The aim of this study was to evaluate the cycle threshold (Ct) values of self-collected vaginal samples as a triage method to colposcopy for high-risk (hr) HPV-positive women. Methods: We analyzed data from GRECOSELF, a nationwide observational cross-sectional study on HPV primary cervical cancer screening in Greece. Self-collected vaginal samples were tested with the cobas^® HPV test (Roche^® Molecular Systems, Pleasanton, CA, USA). The Ct value, i.e., the number of cycles needed until DNA amplification occurs exponentially in a PCR, reflects the viral load, and it was evaluated as a triage method to colposcopy for hrHPV-positive women. Results: For CIN2 and more advanced lesions, the Ct value, as a dichotomous variable at a cut-off of 29.7, had 54.8% (95%CI: 38.7-70.2) sensitivity, 35.4% (23.9-48.2) Positive Predictive Value (PPV), 74.2% (66.8-80.8) specificity, and 86.4% (73.6-91.6) Negative Predictive Value (NPV) for HPV16/18, while for other hrHPV types, sensitivity was 26.7% (12.3-45.9), PPV 6.7% (2.9-12.8), specificity 78.8% (75.1-82.2), and NPV 95.0% (92.5-96.8). For CIN3 and more advanced lesions, the NPV for non-HPV16/18 was 97.9 (96.1-99.1). Conclusions: For self-collected vaginal samples of hrHPV-positive women, the Ct value may be used as a triage method to colposcopy. As Ct values inversely reflect the viral loads, they are lower in high-grade CIN and/or carcinoma.