Liquid-based cytology did not outperform conventional Pap tests for detection of cervical cancer

Liquid-based cytology was neither more sensitive nor more specific than conventional Pap tests for detecting cervical cancer precursors.

“The two cytology methods provided similar risk stratification in predicting cervical intraepithelial neoplasia grade 2 or the more rigorous precancer endpoint of CIN3+ at any threshold of cytologic abnormality,” wrote Mark Schiffman, MD, MPH, senior investigator, division of cancer epidemiology and statistics, and Diane Solomon, MD, division of cancer prevention, National Cancer Institute, NIH, in Bethesda, Md, in an accompanying editorial.

The study involved 89,784 women aged 30 to 60 years from the Dutch cervical screening program at family practices. One hundred and twenty-two family practices were assigned liquid-based cytology (n=49,222) and 124 were assigned conventional Pap tests (n=40,562). The primary histological outcome of cervical intraepithelial neoplasia grades 1+, 2+ and 3+ and carcinoma were assessed.

In intention-to-treat analysis, for cervical intraepithelial neoplasia grade 1+, the adjusted detection rate ratio was 1.01 (95% CI, 0.85-1.19). For grade 2+, the rate was 1.00 (95% CI, 0.84-1.20) and for grade 3+, the rate ratio was 1.05 (95% CI, 0.86-1.29). The rate ratio for carcinoma was 1.69 (95% CI, 0.96-2.99).

In the intention-to-treat analysis, cervical intraepithelial neoplasia grade 3+ or severe dysplasia was detected in 2.7% of the liquid-based cytology group and in 3.5% of the conventional Pap test group (P=.22). In per-protocol analysis, detection was 2.9% with liquid-based cytology and 3.3% with Pap test (P=.53).

“Altogether, these findings provide strong evidence that the performance of liquid-based cytology is not superior to that of the conventional Pap test when applied within a well-organized and quality-controlled cervical screening program,” the researchers wrote.

“For those designing rational cervical cancer prevention programs, Siebers et al have convincingly simplified one aspect of a complex health policy puzzle. Physicians and other health professionals can choose either liquid-based cytology or conventional Pap smear as they discuss how cytology fits into the larger picture,” Schiffman and Colomon wrote.

Siebers AG. JAMA. 2009;302:1757-1764.