Introduction In Brazil, the Digene Hybrid Capture II DNA test (HCII CT-ID - Qiagen) is the only molecular test used to identity Chlamydia trachomatis (CT). This test has shown sensitivity and specificity ranging from 93.8%–97.7% and 95.9%–100.0%, respectively, compared to that of culture. However, up to 27.7% of negative results are false. Real time polymerase chain reaction (qPCR) offers both high sensitivity and specificity. The objective of this study is to describe the development, assess the performance, and costs, of a new in-house qPCR assay for the diagnosis of genital chlamydial infection.
Methods Asymptomatic women aged 14–25 years who attended primary health services in Manaus, Brazil, were screened for CT using the HCII CT-ID-test. A subset of cervical specimens were tested using an in-house qPCR and a commercial qPCR (Artus qPCR) as a reference test. A primer/probe based on the sequence of cryptic plasmid was designed. An economic evaluation was conducted from the provider’s perspective. Overall, 292 specimens were tested by both the commercial kit qPCR and the in-house qPCR.
Results The primers and probe designed for the CP target showed specificity, because no cross–reaction was observed for other STI species tested or with the human DNA. We were able to standardise this reaction in 10 µL and 5 µL volumes for the CP and β-actin set primers, respectively. The sensitivity, specificity, positive and negative predictive values of in the in-house qPCR were 99.5% (95% confidence interval [CI]: 97.1–100), 95.1% (95% CI: 89–98.4), 97.4% (95% CI: 94–99.1), and 99.0% (95% CI: 94.5–100), respectively. The cost per case of CT was $0.55 for HCII CT-ID, $1.45 for Artus qPCR and $1.33 for in-house qPCR.
Conclusion In conclusion, we have developed an in-house qPCR to detect cervical CT targeting CP primers. The in-house qPCR method was its lower cost. Findings from this study can help to revise the national recommendation of using HCII CT-ID. The in-house qPCR should be considered as a good candidate for the diagnostic method for screening programs in Brazil.
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