RELIABILITY OF CYTOLOGY TO DETECT CHLAMYDIAL INFECTION IN ASYMPTOMATIC WOMEN

Chlamydia trachomatis is a frequent sexually transmitted disease. The diagnosis of C. trachomatis infection by cytology is controversial. We compared the ability of Papanicolaou (Pap) smears to detect C. tracho matis infection with antigen detection (enzyme immunoassay; EIA) and p olymerase chain reaction (PCR). One hundred sixty-seven women attendin g a therapeutic abortion clinic were enrolled in the study. Endocervic al samples were first collected for EIA and PCR, and then Pap smears w ere prepared for cytologic evaluation. Eight patients were excluded fr om the study due to the lack of an endocervical component. The criteri a established by Gupta and associates (Diagn Cytopathol 1988;4:224-229 ; Acta Cytol 1979;23:315-320) were used in this study to assess the sp ecificity and sensitivity of the Pap smear in recognizing C. trachomat is infection. After EIA testing, the remaining sample was subjected to phenol-chloroform extraction to purify the DNA and then tested by PCR . Positive PCR samples were subjected to repeat phenol-chloroform and retested to confirm the positive result. Using a confirmed PCR or a bl ocked EIA as the extended gold standard, the incidence of C. trachomat is infection was 9.4%. Fifteen of the 159 cases reviewed were positive by extended gold standard. Thirteen (86.7%) of those 15 cases were in terpreted as negative by cytology (false-negatives), and two (13.3%) c ases were positive. Of the remaining 144 cases, 14 cases (9.7%) were i nterpreted as positive by cytology (false-positives) but were not conf irmed by the extended gold standard. Ten (66.7) of the 15 cases confir med by the extended gold standard were interpreted as negative by EIA (false-negatives), and five (33.3%) were positive. There were no false -positive by EIA. In this study, the sensitivity and the specificity f or cytology were 13.3% and 90.3%, respectively. The positive predictiv e value was 12.5%, and the negative predictive value for cytology was 90.9%. The sensitivity and the specificity for EIA were 33.3% and 100% , respectively. The positive predictive value was 100%, and the negati ve predictive value for EIA was 93.5%. Both EIA and cytology are insen sitive methods compared with PCR. Based on these data, cytology should not be used to diagnose C. trachomatis infection in an asymptomatic f emale population with a moderate risk of C. trachomatis infection. (C) 1997 Wiley-Liss, Inc.