Does acetic acid influence the non-dysplastic Pap smear?

Effect of glacial acetic acid pre-treatment of cervical liquid-based cytology specimens on the molecular detection of human papillomavirus

OBJECTIVE

Cytology laboratories routinely treat cervical liquid-based cytology (LBC) specimens that are heavily contaminated with blood with glacial acetic acid (GAA) in order to lyse red blood cells and facilitate assessment. However, the impact on downstream human papillomavirus (HPV) detection is not well understood. This study examines the effect of GAA pre-treatment of ThinPrep(®) Preservcyt(®) specimens on the molecular detection of HPV.

METHODS

A panel of 150 routinely collected cervical LBC specimens was tested with two commercial HPV tests, the Abbott RealTime High Risk HPV test (rtHPV) and the Qiagen Hybrid Capture 2 High Risk HPV DNA test (HC2), as aliquots before and after GAA treatment. Statistical analysis was performed using McNemars test and Bland and Altman plots.

RESULTS

Agreement between the results of the rtHPV test on GAA-untreated and GAA-treated specimens was 95.7%, with no evidence of a significant difference in the distribution of the discrepant results (P = 0.414). HC2 test agreement on GAA-untreated and GAA-treated specimens was 91% at a cut-off of 1 relative light unit index (RLUI) and 92% at a cut-off of 2 RLUI. There was no evidence of a difference in the distribution of discordant results at a cut-off of 1 (P = 0.405) and 2 RLUI (P = 0.564).

CONCLUSIONS

GAA pre-treatment of cervical ThinPrep Preservcyt LBC specimens had little effect on the two commercial HPV tests used in this study. The impact of GAA treatment on HPV testing should, however, be validated for all HPV tests and all LBC collection media used in each particular diagnostic setting.