Improved detection of Chlamydia trachomatis in endocervical samples by using a new polymerase chain reaction assay

To compare the performance of a commercially developed polymerase chain reaction (PCR) assay, Amplicor Chlamydia trachomatis from Roche Molecular Systems, with that of a standard enzyme immunoassay (EIA) system, Chlamydiazyme from Abbott Laboratories, which is currently used throughout New Zealand.

Cervical swabs were collected from 819 female patients attending the family planning clinic in Christchurch. These swabs were then analysed using the Amplicor and Chlamydiazyme assays.

The prevalence of chlamydia infection was 4.2% by the Chlamydiazyme EIA method and 5.3% with the Amplicor PCR assay. In 20 cases, where the results from the two assays were discordant, the conflict was 'resolved' by using a third assay which detects a separate region of the chlamydia genome. This gave an overall prevalence of 5.8% of confirmed infections in this group. The Amplicor PCR assay detected 29.4% more cases than the usual EIA method.

This study demonstrates that Amplicor PCR assay allows improved identification of C trachomatis infections in a population with a relatively low prevalence of infection. The Amplicor PCR assay detects a significant number of additional infections and should be considered for routine use. As the PCR assay is more expensive a shift in the price/payment structure may be required before this assay comes into widespread use. However, the reduced morbidity resulting from the detection and treatment of otherwise unrecognised cases should also be considered in any cost benefit analysis.