Comment: The quality of evidence is downgraded by inconsistency (unexplained variability in results).
A systematic review included 94 studies of the conventional Pap test and 3 studies of monolayer cytology with a total of 22 412 subjects. No studies of computerized screening were included. Data were organized by cytologic and histologic thresholds used to define disease. For conventional Pap tests, estimates of sensitivity and specificity varied greatly in individual studies. In the 12 studies with the least biased estimates, sensitivity ranged from 30% to 87% and specificity ranged from 86% to 100%.