Evidence of labile inhibitors in the detection of Chlamydia trachomatis in cervical specimens by polymerase chain reaction

A total of 276 cervical swabs (241 from first visits and 35 from follow-up visits) from 241 women were tested for Chlamydia trachomatis by polymerase chain reaction (PCR) and enzyme immunoassay (EIA). Sixty-one smears (53 from first visits and 8 from follow-up visits) from 53 women were stained by direct fluorescent antibody (DFA). Twenty-one (8.7%) women had positive swabs in at least two different tests. All follow-up swabs (collected between 3 days and 3 weeks after the first clinical visit) were positive in at least one test when the woman had been positive at the first visit and no antibiotic treatment had been initiated. Including swabs from follow-up visits and DFA results, the respective sensitivities and specificities of the assays were as follows: PCR, 75.9% and 100%; EIA, 69% and 98.4%. The seven swabs that were false negative by PCR (tested initially after thawing from -20 degrees C) were mailed nonrefrigerated to the assay manufacturer, where they tested true positive. These data point to labile inhibitors of the PCR, predominantly cervical mucus.