A comparative analysis of cycle threshold (Ct) values from Cobas4800 and AmpFire HPV assay for triage of women with positive hrHPV results.

Background: To compare the triage performance of HPV viral loads reflected by cycle threshold values (CtV) from two different HPV testing assays: the PCR based Cobas4800 and the isothermal amplification based AmpFire assay.

Methods: We used the data from a sub-study of The Chinese Multi-Center Screening Trial and analyzed the data of the cases positive in both Cobas4800 and AmpFire assays with recorded CtV. Spearman's correlation was applied to analyze the association between CtV from AmpFire and Cobas4800 assays, as well as the correlation between CtV and the histological lesion grades. The 50th percentile of CtV was used as the cutoff to construct triage algorithms for HPV-positive cases. McNemar's test was used to analyze the differences in sensitivity and specificity for detecting CIN2 + and CIN3 + in different triage algorithms.

Results: Four hundred forty-six HPV positive women who had consistent HPV results from Cobas4800 and AmpFire in terms of the HPV genotype and reported Ct values were included in the analysis. The mean CtV of hrHPV tested by Cobas4800 and AmpFire were linear correlated. Direct association were showed between the severity of cervical lesions and the HPV viral loads reflected by CtV of hrHPV, HPV16, non-16/18 hrHPV and A9 group from both assays. HPV16/18 genotyping combined with low-CtV for non-16/18 hrHPV, especially A9 group, were demonstrated to be satisfactory in the sensitivity and specificity for detecting CIN2 + or CIN3 + .

Conclusion: Ct value represented a good triage marker in both PCR-based and isothermal amplification HPV detection.