The effectiveness of acetic acid wash protocol and the interpretation patterns of blood contaminated cervical cytology ThinPrep(®) specimens.

Background: ThinPrep(®) (TP) cervical cytology, as a liquid-based method, has many benefits but also a relatively high unsatisfactory rate due to debris/lubricant contamination and the presence of blood. These contaminants clog the TP filter and prevent the deposition of adequate diagnostic cells on the slide. An acetic acid wash (AAW) protocol is often used to lyse red blood cells, before preparing the TP slides.

Design: From 23,291 TP cervical cytology specimens over a 4-month period, 2739 underwent AAW protocol due to initial unsatisfactory smear (UNS) with scant cellularity due to blood or being grossly bloody. Randomly selected 2739 cervical cytology specimens which did not undergo AAW from the same time period formed the control (non-AAW) group. Cytopathologic interpretations of AAW and non-AAW groups were compared using the Chi-square test.

Results: About 94.2% of the 2739 cases which underwent AAW were subsequently satisfactory for evaluation with interpretations of atypical squamous cells of undetermined significance (ASCUS) 4.9% (135), low-grade squamous intraepithelial lesions (LSIL) 3.7% (102), and high-grade squamous intraepithelial lesions (HSIL) 1% (28). From the 2739 control cases, 96.3% were satisfactory with ASCUS 5.5% (151), LSIL 5.1% (139), and HSIL 0.7% (19). The prevalence of ASCUS interpretations was similar (P = 0.33). Although there were 32% more HSIL interpretations in the AAW group (28 in AAW vs. 19 in non-AAW), the difference was statistically insignificant (P = 0.18). AAW category; however, had significantly fewer LSIL interpretations (P = 0.02). The percentage of UNS cases remained higher in the AAW group with statistical significance (P < 0.01).

Conclusions: While AAW had a significantly higher percent of UNS interpretations, the protocol was effective in rescuing 94.2% of specimens which otherwise may have been reported unsatisfactory. This improved patient care by avoiding a repeat test. The prevalence of ASCUS and HSIL interpretations between AAW and non-AAW groups were comparable. Though not statistically significant, HSIL interpretations were relatively higher in the AAW group. LSIL interpretations showed lower prevalence in AAW group.