High rates of atypical cervical cytology: occurrence and clinical significance.

The current literature suggests that atypical (benign atypia or class II) Papanicolaou smears occur at a frequency of 1.6-5.4% and are associated with a substantial rate of underlying cervical dysplasia. However, we noted that our rate of atypia exceeded these figures, particularly in our clinic population. To quantify this observation, 1107 consecutive Papanicolaou smears from the clinic population were audited prospectively and compared with 262 consecutive Papanicolaou smears performed contemporaneously in private patients served by the same laboratory. The rate of histologic dysplasia underlying this diagnosis was assessed by analyzing the results of 101 consecutive colposcopic examinations performed subsequently on clinic patients evaluated for persistently atypical cytology (atypical index smear followed by repeat cytology scheduled 2-4 months later). The prevalence of atypia in the clinic population was 321 of 1107 (29%; 95% confidence interval [CI] 26-32%), a rate 2.3 times that of the private patients (33 of 262, 13%) (P less than .001). Eighteen of 101 clinic patients with persistent atypia had dysplasia (18%; 95% CI 11-25%), and 25 of 101 (25%; 95% CI 17-33%) had human papillomavirus infection, both documented by the histology of directed cervical biopsies. Cervical intraepithelial neoplasia grade II or higher was present in three of these 18 women (17%; 95% CI 6-39%). We conclude that some populations have atypical cervical cytology at a frequency much greater than that reported previously. Furthermore, the pathology underlying this diagnosis is considerable and warrants evaluation. The optimal management of atypical cervical cytology in such populations is problematic.