The superiority of polymerase chain reaction over an amplified enzyme immunoassay for the detection of genital chlamydial infections

Abstract

Background/objectives: The polymer conjugate enhanced enzyme immunoassay (IDEIA) and Cobas Amplicor polymerase chain reaction Chlamydia trachomatis (CT) (Amplicor PCR) are two commonly used assays for the diagnosis of CT infection. The performance of these assays was compared for the diagnosis of genital CT infection among 1000 consecutive patients attending a genitourinary medicine (GUM) clinic. Confirmation of positive results and the clinical significance of the absence of cryptic plasmid in chlamydia on the diagnosis of infection by Amplicor PCR were also investigated. Methods: IDEIA, Amplicor PCR, and two nested in-house PCR assays targeting cryptic plasmid and omp1 gene were performed on all samples. DNA from Amplicor PCR negative samples was pooled for in-house PCR assays. Each pool contained DNA from seven Amplicor PCR negative samples. Results: Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and efficiency of IDEIA in the diagnosis of genital CT infection were 80%, 97%, 80%, 97%, and 95%, respectively. Sensitivity, specificity, PPV, NPV and efficiency of Amplicor PCR were 99%, 98%, 89%, 100%, and 98%, respectively. 16 (11%) of 144 Amplicor PCR positive results were identified as false positive by in-house PCR assays. No isolate of plasmid free CT was detected among the study population. Conclusions: IDEIA should not be used for the diagnosis of CT infection because of its poor sensitivity. Although the analytic specificity of Amplicor PCR was 98%, because of the adverse medical, social, and psychological impact of false positive results for patients, confirmation of Amplicor PCR positive results by a different assay with comparable sensitivity is essential. Amplification assays targeting cryptic plasmid are appropriate for the diagnosis of genital CT infections.

Comparative performance of the Roche COBAS Amplicor assay and an in-house real-time PCR assay for diagnosis of Chlamydia trachomatis infection

“…The availability of DNA and data about the accurate diagnosis of C. trachomatis infection among 1000 consecutive patients saved the cost and labour of sample collection, DNA extraction, IHNCP-PCR, IHNMOMP-PCR and Amplicor PCR. As all samples were coded before IHRT-PCR, the use of data and samples which were collected for a previous study was justified (Jalal et al, 2006a). IHRT-PCR missed three positive samples while Amplicor PCR missed one.…”

“…Genital swabs were collected with the IDEIA chlamydia collection kit, and DNA was extracted using the MagNA Pure LC total nucleic acid isolation kit and MagNA Pure LC Robot. Three different PCR assays were performed on each sample in the previous study: Amplicor PCR, in-house nested cryptic plasmid PCR (IHNCP-PCR) and in-house nested major outer membrane protein PCR (IHNMOMP-PCR) (Jalal et al, 2006a). The data from the previous study and the results generated by this study were used to investigate the comparative performance of IHRT-PCR and Amplicor PCR for the diagnosis of C. trachomatis infection.…”

“…Due to the limited quantity of stored DNA, 5 ml DNA instead of 10 ml from each sample was used per reaction. These samples were obtained from a cohort of patients described previously (Jalal et al, 2006a). Briefly, the cohort included 1000 consecutive patients attending the genitourinary medicine clinic, in late 2003, at Addenbrooke's Hospital, Cambridge.…”

“…Accurate and timely diagnosis of infection is essential not only for the treatment of infected individuals but also to reduce the transmission of infection among the sexually active population. Nucleic acid amplification tests (NAATs) have demonstrated their superiority over antigen detection and cell culture for screening as well as for the diagnosis of C. trachomatis infection (Østergaard, 1999;Jalal et al, 2006a).…”

The Implementation of European Association of Urology Guidelines in the Management of Acute Epididymo-Orchitis

“…Chlamydia PCR is not yet widely available for routine clinical use but is rapidly becoming a gold standard test due to its high specificity and sensitivity. 9 Interestingly, 28% of patients were already prescribed antibiotics at the time of presentation having attended a primary care centre prior to their attendance at the emergency department. The choice of antibiotics prescribed in the primary care setting was varied ( Table 2).…”