Development and Validation of a Preanalytic Procedure for Performing the cobas HPV Test in SurePath Preservative Fluid

The formation of chemical cross-links between nucleic acids and proteins in formalin-containing media presents challenges for human papillomavirus (HPV) testing of cervical samples collected in SurePath Preservative Fluid. A preanalytic process involving addition of a nucleophilic buffer and heating the sample to 120°C was developed to reverse the effects of cross-linking and improve nucleic acid accessibility for the cobas HPV Test in SurePath. Cycle threshold (CT) values for cobas HPV detection were evaluated over time and various temperatures, and mean CT differences between pretreated and both untreated SurePath samples and those collected in PreservCyt were assessed. Without pretreatment, low viral levels (1 × limit of detection) of HPV were no longer detectable by 7 days. For prospectively collected specimens, mean (95% CI) CT differences between pretreated and untreated samples indicated enhanced HPV DNA recovery in all categories of treated samples: −2.58 (−3.16 to −2.01), −2.63 (−3.62 to −1.64), and −3.39 (−4.95 to −1.82), respectively, for other 12 high-risk HPV types, HPV16, and HPV18. Furthermore, mean (95% CI) CT differences of pretreated SurePath samples were comparable to simultaneously collected PreservCyt samples: −0.48 (−0.98 to 0.02) and −0.23 (−0.93 to 0.46), respectively, for HPV16 and HPV18; a borderline significant difference [−0.35 (−0.57 to −0.13)] was observed for other 12 high-risk HPV types. This preanalytic procedure therefore ensures a validated, safe, and accurate method for cobas HPV testing in SurePath.