Update on the Papanicolaou smear: new issues for the 1990s.

The Papanicolaou (Pap) smear is a complex examination that has undergone refinement in recent years. It is now widely accepted that a false-negative rate of perhaps 10 to 20% is inevitable for a variety of reasons. The diagnosis of "atypical cells of undetermined significance" is not a benign diagnosis and is often followed by a more severe lesion on follow-up. The Pap smear appears to be an inefficient method for detecting glandular neoplasms, and clinical features remain the most important diagnostic clue. A Pap smear and cervical biopsy should correlate in 75% or more of cases. In cases of noncorrelation, a positive Pap smear diagnosis is supported in the vast majority of cases.