Performance of a commercial polymerase chain reaction test for endocervical Chlamydia trachomatis infection in a university hospital population

Abstract

Objectives: To examine the accuracy of a commercial polymerase chain reaction (PCR) test (Amplicor CT R , Roche Diagnostic Systems, Branchburg NJ) for identification of endocervical chlamydial infections through both laboratory evaluation and among a diverse teaching hospital patient population.Methods: Testing of reliable threshold inocula and reproducibility were carried out using laboratory stock organisms. Paired endocervical samples from patients with a wide range of indications were tested by PCR and an established culture procedure, and discrepant pairs were further analyzed to determine true results.Results: Laboratory evaluation suggested that one copy of target DNA from a viable organism consistently yielded a positive result, and test reproducibility was very good, with an overall coefficient of variation of 15%. Compared to true results in 1,588 paired clinical samples from 1,489 women with a 10% prevalence of infection, the PCR test and culture yielded respective sensitivities of 87.4% and 78.0%, and negative predictive values of 98.6% and 97.6%. Specificity and positive predictive value for both tests were 100%. Cost per specimen was nearly identical at $18.84 and $18.88 respectively. Polymerase inhibitors and organisms lacking target DNA were not found in false-negative PCR samples.Conclusion: This commercial PCR test is accurate, cost-competitive, and much faster than culture for diagnosis of endocervical chlamydia infections in our population of intermediate prevalence of chlamydial infection. Infect. Dis. Obstet. Gynecol. 6:224-229, 1998.

Evaluation of COBAS AMPLICOR (Roche): Accuracy in Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by Coamplification of Endocervical Specimens

“…We calculated the direct costs of CA for each C. trachomatis and N. gonorrhoeae result to be $9.09, including labor ($2.00 at $16/h), reagents ($6.69), and equipment ($0.40). The cost of each result from C. trachomatis culture has been previously calculated to be $18.88 (8).…”

“…They were transported per the protocol of the Jembec system to the laboratory, incubated in 5% CO 2 , and examined for typical colonies at 24, 48, and 72 h. Colonies with oxidase activity, gram-negative diplococci, and a positive Gonogen II (sensitivity, 98%; Becton Dickinson, Franklin Lakes, N.J.) reaction were reported as positive for N. gonorrhoeae; otherwise colonies were reported as negative. Chlamydia cultures were performed as pre-viously described (7,8), using aliquots from the specimen in 2SP medium prior to its use in the CA system. Briefly, our culture procedure uses centrifugeassisted inoculation of the specimen onto McCoy cell monolayers on coverslips in shell vials, incubation at 37°C in 5% CO 2 , inhibition of cellular energy use by cycloheximide, one blind passage, iodine staining, and examination at ϫ400 magnification for typical chlamydia inclusions by strict criteria (1).…”