Underdiagnosis of Chlamydia trachomatis Infection: Diagnostic Limitations in Patients with Low-level Infection

To determine limitations in commonly used methods for detection of Chlamydia trachomatis, 601 genitourinary specimens from patients in a sexually transmitted disease clinic were examined with quantitative cultures and by 2 different direct antigen tests, immunofluorescence (Micro Trak; Syva Company, Palo Alto, CA) and enzyme immunoassay (Chlamydiazyme; Abbott Laboratories, North Chicago, IL). Genital specimens were held no longer than 5 hours (at 4°C) prior to inoculation for culture; 28% (168/601) were positive. To evaluate the effect of storage on culture efficacy, duplicate specimens were also stored at -70°C and brought out subsequently for culture a second time. Only 32% (8/25) of specimens cultured within 5 hours and having 100 inclusions; 50% (22/44) with 00 inclusions; and only 11% (6/53) with