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Validation of the Roche COBAS Amplicor system for Chlamydia trachomatis
J M Matthews-Greer1, K L McRae, E B LaHaye
1Diagnostic Virology Laboratory, Louisiana State University Health Sciences Center at Shreveport, 1501 Kings Highway, Shreveport, LA 71130-3932, USA. jgreer@lsuhsc.edu
Objective:
Validation of the Roche Amplicor polymerase chain reaction (PCR) using the Comprehensive Bio-Analytical System (COBAS) automated PCR analyzer in our laboratory.
Design:
Endocervical swab specimens for both EIA and PCR were collected from a total of 193 women. EIA for chlamydia was performed using the MicroTrak Chlamydia Kit (Wampole Labs, Cranbury, NJ). PCR was performed using Roche Amplicor reagents on the COBAS instrument.
Setting:
Louisiana State University Health Sciences Center at Shreveport, Shreveport LA.
Patients:
All cervical swab specimens, (n = 193), collected from patients presenting either to the Women's Health or Primary Care Clinic (Obstetrics and Gynecology and Family Practice) were included in this study.
Results:
Most of the specimens, 138/193 or 71.5%, tested negative by both techniques. Three of the 193 specimens, 1.5%, were inhibitory for PCR since the internal control was negative. Fifty-one specimens, 26.4%, tested positive by both techniques or by PCR alone. No specimens were positive by EIA only. Twenty-eight of the 51 were positive by both methods, (14.5% of the total tested; 54.9% agreement among the specimens testing positive). An additional 23 were positive by PCR alone, i.e., 11.9% total discrepant positive specimens; 45% discordant results among the specimens testing positive). Seventeen PCR-positive specimens divided among four separate runs were retested by PCR. Of these, 15 were repeat positive, giving the test a reproducibility of 88.2%.
Conclusions:
Our results concur with previously published comparison data for EIA and PCR testing. We conclude that the PCR should detect a significantly increased number of chlamydia infections among our LSUHSC-S population, but there are drawbacks to using this technique. Specimen preparation time for PCR is almost twice as long as EIA, and the Roche PCR assay is not licensed for ocular specimens as is our EIA procedure. In addition, since neither technique is accepted for testing for medicolegal purposes, we must continue the use of culture for cases of suspected sexual abuse.
