Evaluation of sensitivity of 10 diagnostic assays for Chlamydia trachomatis by use of a simple laboratory procedure.

AIMS

To determine the sensitivity of commercially available diagnostic assays for Chlamydia trachomatis using a simple method.

METHODS

Nine commercial assays and an "in-house" polymerase chain reaction (PCR) were evaluated using serial dilutions of a laboratory grown H serovar--four of them using a laboratory grown E serovar. Seven of the assays were further tested using dilutions of several cervical samples known to contain chlamydiae.

RESULTS

The most sensitive assays were the MicroTrak direct fluorescent antibody (DFA) test (Syva) and the PCR which detected C trachomatis at a 10(-8) dilution of the H serovar, while the two least sensitive, Clearview (Unipath) and TestPack (Abbott), were positive only at 10(-4) and-3 dilutions, respectively. A range of enzyme immunoassays (EIAs) and a nucleic acid hybridisation test were of intermediate sensitivity. The results with serovar E were consistent with these. When clinical samples were examined, the DFA test detected C trachomatis in dilutions at least 10-fold greater than any other assay.

CONCLUSIONS

The range of sensitivity of diagnostic assays determined by the laboratory dilution procedure is very wide. Sensitivity assessed in this way, however, reflects the ability of the assays to detect C trachomatis in large scale clinical trials. The dilution procedure, which is simple to undertake, could therefore be applied by any laboratory before a new diagnostic method is considered for routine use.