DETECTION OF CHLAMYDIA-TRACHOMATIS BY DIRECT FLUORESCENT-ANTIBODY STAINING - RESULTS OF THE COLLEGE-OF-AMERICAN-PATHOLOGISTS PROFICIENCY TESTING PROGRAM, 1986-1992

Since 1986 the College of American Pathologists has provided a profici ency testing program for laboratories that use the direct fluorescent antibody test for direct detection of Chlamydia trachomatis in clinica l specimens. The number of survey participants increased from about 20 0 in 1986 to about 800 in 1992, and in all years the majority used rea gents produced by Syva Co (Palo Alto, Calif), although the percentage decreased from 82% in 1986 to 68% in 1992. Performance on positive spe cimens varied based on specimen fixation method, number of elementary bodies present, serotype, and specific product used, and declined when the specimen was fixed with acetone prior to shipping or contained fe wer than 50 elementary bodies, particularly when the elementary bodies were of serotype L(2). Performance with negative specimens was also v ariable, with 79% to 96% of all participants, and over 90% since 1991, responding correctly. In the last 1992 survey, an ungraded specimen ( a five-well slide containing latex beads incorporated with fluorescein isothiocyanate) and a questionnaire were included to assess the poten tial influence of laboratory operations on performance. Responses to t he questionnaire and the ungraded specimen suggested that the level of experience of testing personnel affected performance. A test for tren d in error rate across the number of years that a laboratory had offer ed the Chlamydia direct fluorescent antibody test indicated that error rate declined as degree of experience with the test increased.