Direct immunofluorescence for Chlamydia trachomatis on urogenital smears for epidemiological purposes

A population of 197 asymptomatic women, attending an out-patient department for birth-control advice, was screened for urogenital infection with Chlamydia trachomatis by direct immunofluorescence on cervical and urethral smears. A blood sample was obtained for chlamydial serology and demographic, behavioural and clinical data were recorded. Eleven (5.5%) women had a chlamydial infection. Chlamydial infection, as diagnosed with direct immunofluorescence, correlated with a history of sexually transmitted disease (p less than 0.01), promiscuity (p less than 0.01), use of oral contraceptives (p less than 0.02) and high chlamydial antibody titres (p less than 0.01). These last also correlated with a history of sexually transmitted disease (p less than 0.02) and promiscuity (p less than 0.02). These results, obtained with direct immunofluorescence, are indistinguishable from those obtained previously with chlamydial culture. Direct immunofluorescence on urogenital smears seems a valuable tool for epidemiological investigation. Our data also support the hypothesis that oral contraceptive use is correlated with chlamydial infection because of increased cervical susceptibility to infection and not because of a sampling bias towards oral contraceptive users.