Differences in the Prevalence of Chlamydia trachomatis Reported by Two Laboratories Using the Direct Immunofluorescence Test

To the Editor. — Over a two-year period, unforeseen circumstances led us to use two different microbiology laboratories for Chlamydia trachomatis testing by the direct immunofluorescence method. The large disparity in the results obtained from the two laboratories illustrates the need for standards to ensure the quality of this test.

Study.— Between January 14, 1985, and April 29, 1985, we tested patients with and without cervicitis for the presence of C trachomatis using the direct immunofluorescence test. Patients were seen in three family practice offices and a family planning center. The testing was performed at a private microbiology laboratory in Salt Lake City. The rate of detection of C trachomatis in the patients with and without symptoms of pelvic infection was 3% (6/194). After the study was concluded, the direct testing for C trachomatis infections in our family practice center reverted to a local laboratory we had used previously. Surprisingly,