Diagnostic efficacy of chlamydial antibodies in cervical secretions from pregnant women and adolescent girls.

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Abstract
To assess the prevalence of cervical antibodies to Chlamydia trachomatis in two different populations and to correlate the findings to culture, direct fluorescent antibody test (DFA) and serum antibodies. Antenatal clinics and clinic for teenage counselling in Gävle. 1078 pregnant women attending for routine follow up in the third trimester of pregnancy and 256 teenage girls. Cervical IgG and IgA antibodies to Chlamydia trachomatis. Cervical cultures for chlamydia. Serum IgG antibodies. DFA tests were used only in the teenage group. The prevalence of positive culture was 2.0% in pregnant women and 8.6% in teenage girls. In pregnant women cervical IgG > or = 8 and IgA > or = 8 were found in 7.2% and 5.8% respectively and in teenage girls in 6.6% and 2.0% respectively. The agreement between cervical IgG > or = 8 and humoral IgG > or = 32 was 0.76 in the pregnant group and 0.95 in the teenage group. The sensitivity, specificity and positive predictive value (PPV) for cervix IgG > or = 8 to predict a positive culture was 0.64, 0.94 and 0.18 respectively in pregnant women and 0.41, 0.97, 0.53 respectively in teenage girls. Of 31 teenage girls with either positive culture or positive DFA 12 had cervical IgG > or = 8 while five of 225 with negative chlamydia tests had cervical IgG > or = 8 (sensitivity 0.40 and PPV of 0.71). Cervical IgG > or = 16 was found in eight of 31 with positive chlamydia tests and in one of 225 with negative tests (sensitivity 0.26 and PPV 0.89). The finding of cervical IgG > or = 16 predicts current chlamydia (culture or DFA) in nearly 90% in a teenage population. It might indicate current infection in spite of negative culture in some cases. For low titres and in a low prevalence pregnant population cervical IgG are not useful for the diagnosis of chlamydia. As the sensitivity is low cervical antibodies cannot be used for screening purposes.