In Slovenian cervical cancer screening program ZORA, Qiagen HPV test Hybrid Capture 2 (HC2) is used for a triage of women with low-grade cytology and as test of cure since 2011. For these analyses cervical samples are collected in Standard Transport Medium (STM), Qiagen. The major disadvantages of STM are poor preservation of cell morphology and high cost. In-house liquid based medium (LBM) is already extensively used in routine laboratory practice for immunocytochemical and molecular tests at the Institute of Oncology Ljubljana and in some other Slovenian laboratories. It is cheaper than STM and enables both morphological and molecular analysis. Routine use of in-house LBM in the national cervical cancer screening programme would allow a single sampling procedure for both liquid based cytology and HPV testing. However, the new medium might affect results of hrHPV analysis. The aim of the study was to compare and validate in-house LBM toward the STM for detection of hrHPV with HC2.
In 183 women (aged from 20 to 64 years, 38.3 on average) referred to colposcopy two cytological cervical samples were taken prior colposcopy by physician at the colposcopy clinic. First cytological sample was taken with endocervical brush and Ayer spatula for PAP smear, after that both devices were stored in in-house LBM; second was taken with Qiagen brush and stored in STM. Cytological samples in different media were analysed on hrHPV by HC2 at cut-off value RLU/CO = 1.0. Results were compared and then validated against the worst histology result from the screening registry within one year since the samples were collected.
HPV-positivity rate was higher in in-house LBM (135/183, 73.8%) than in STM (128/183, 69.9%). Agreement of results was excellent (174/183, 95.1%; Kappa = 0,879 (p < 0.001). Test performance was comparable, however STM had slightly higher sensitivity for CIN2+ (95.5 vs. 96.6%) as well as specificity (46.8 vs. 55.3%), NPV (91.7 vs. 94.5%) and PPV (63.0 vs. 67.2%). Among 9 discordant cases, 1 case was HPV negative in in-house LBM but positive in STM and 8 cases were HPV positive in in-house LBM but negative in STM. 89/183 (48.6%) women had CIN2+.
Comparable HPV-positivity rate, agreement of HPV analyses, sensitivity, specificity, PPV and NPV for CIN2+ between the two media suggest that in-house LBM could be used for hrHPV testing instead of STM to reduce costs and preserve morphology. However, larger prospective study on screening population has to be performed to confirm this assertion.