The accuracy of the Papanicolaou smear in the screening and diagnostic settings

We evaluated the performance of the Papanicolaou smear in screening and diagnostic settings.

We analyzed Papanicolaou smear results of 1,850 women recruited into a clinical trial to evaluate an emerging technology for the detection of cervical cancer. Screening and diagnosis groups were based on the history of previous Papanicolaou smear results. We calculated sensitivities, specificities, positive and negative likelihood ratios (LR+ and LR-), receiver operating characteristic curves, and areas under the receiver operating characteristic curve (AUC).

In the screening group, by defining disease as cervical intraepithelial neoplasia (CIN) 2,3/cancer or worse and using high-grade squamous intraepithelial lesion (HSIL) as the test cutpoint, the AUC was 0.689, and the LR+ and LR- were 39.25 and 0.67, respectively. In the diagnosis group, the AUC was 0.764, and the LR+ and LR- were 3.79 and 0.56, respectively. By defining disease as human papillomavirus/CIN 1 or worse and HSIL as the test cutpoint, the AUC was 0.586, and the LR+ and LR- were 17.01 and 0.92 in the screening group; in the diagnosis group, the AUC was 0.686, and the LR+ and LR- were 2.77 and 0.75, respectively.

In a screening setting, a Papanicolaou smear result of HSIL or worse is 39 times more likely in a patient with CIN 2,3/cancer than in a patient without it. This compares to 4 times more likely in the diagnostic setting. The magnitude of the positive likelihood ratio observed in the screening group indicated that abnormal Papanicolaou smear results obtained in the screening setting should have more impact on clinical decision making than those from results obtained in the diagnostic setting.