[Use and yield of microbiological diagnosis of sexually transmitted Chlamydia trachomatis infections in Vestfold 1984-93].

Testing for Chlamydia trachomatis has become widely available in Norway during the last ten years. We have evaluated the number and yield of tests in Vestfold county. The number of performed tests increased from 0.6 per 100 inhabitants in 1984 to 6.5 in 1993, while the yield declined from 14.7% to 3.4%. The incidence of diagnosed infection declined from 4.0 per 1,000 person-years in 1988 to 2.2 in 1993. In 1991, 59.6% of the samples were taken from women aged 15 to 29 years. Male patients provided 7.1% of the samples. Between 40 and 50 tests were performed among every 100 Vestfold women in their twenties. More than three quarters of the positive tests were found in women under 25 years of age or in men. Women 30 years of age or older accounted for 32.4% of the tests, but only 9.3% of the positive tests; reaching a yield of less than 1.1%. We recommend that doctors perform fewer screening tests in women older than 25 years and more tests in men following notification by partner. This will increase the yield and reduce the number of false positive tests.