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Report: Liquid-based cytology is “not superior” to the Pap

A study finds that the two test methods detect cervical intraepithelial neoplasia at a comparable rate

November 2009 · Vol. 21, No. 11

Liquid-based cytology is not superior to the Pap test in the detection of cervical cancer precursors. So says a study by Albertus G. Siebers, MSc, and colleagues published in the October 28 issue of The Journal of the American Medical Association. 1

The randomized, controlled trial of 90,000 women, 30 to 60 years old, was conducted at 246 practices in the Netherlands. Of these, 122 (comprising 49,222 patients) were randomly assigned to perform cervical cancer screening using liquid-based cytology, and 124 (40,562 patients) were assigned to conduct screening using the Pap test. Subjects were followed for 18 months.

The adjusted detection-rate ratio for cervical intraepithelial neoplasia (CIN) 1+ was 1.01 (95% confidence interval [CI], 0.85–1.19); 1.00 for CIN 2+ (95% CI, 0.84–1.20); and 1.05 for CIN 3+ (95% CI, 0.86–1.29). The adjusted detection-rate ratio for carcinoma was 1.69 (95% CI, 0.96–2.99).

The adjusted ratio for positive predictive value, considered at several cytologic cutoffs and for various outcomes of CIN, did not differ significantly from unity, the researchers determined.

“Because of randomization, it can plausibly be assumed that the prevalence of CIN was equal in both study groups,” write Siebers and colleagues. “Therefore, the lack of difference in detection rates and PPV in this trial demonstrates that liquid-based cytology is neither more sensitive nor more specific in detecting cervical cancer precursors than the conventional Pap smear.”

“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.”

Reference

1. Siebers AG, Klinkhamer PJJM, Grefte JMM, et al. Comparison of liquid-based cytology with conventional cytology for detection of cervical cancer precursors: a randomized controlled trial. JAMA. 2009;302:1757-1764.

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