Background: TTANGO (Test, Treat ANd GO) will measure the clinical effectiveness, cost-effectiveness, and acceptability of a molecular-based point-of-care (POC) test (GeneXpert) for chlamydia (CT) and gonorrhoea (NG) infections in remote Australian Aboriginal communities. TTANGO is a crossover randomised control trial, with 12 participating primary health care centres; six services will use POC in year 1, and the other six in year 2. Services not using POC will maintain standard practice in each year. Routine reference laboratory tests for CT and NG will continue throughout the trial in both study arms.
Methods: Since June 2013, five of the six sites have been randomised to using the GeneXpert CT/NG test. We describe the sensitivity and specificity of the GeneXpert CT/NG test compared to routine laboratory NAAT tests.
Results: Of the 444 POC tests performed, the sensitivity and specificity of the GeneXpert test for CT infection was 100% (95%CI:92.3-100.0) and 99.2% (95%CI:97.8-99.8), respectively and for NG infection the sensitivity and specificity was 100% (95%CI:88.4-100.0) and 100% (95%CI:99.1-100.0), respectively. There were three discordant CT results which were positive on GeneXpert and negative on the laboratory NAAT test. There were 25 errors (5.6% of all tests) predominately due to operator error in sample preparation; repeat testing of all samples gave valid results. Further errors have been minimised with training and/or changes to the sample transfer device (plastic pipette to syringe).
Conclusions: The sensitivity and specificity of the GeneXpert CT/NG test is both excellent and consistent with laboratory and field evaluations. An updated sensitivity and specificity estimate will be provided in June 2014. The uptake of CT and NG testing generally has been higher than expected, possibly related to initial enthusiasm surrounding the use of this new technology and increased awareness about STI screening during trial implementation. Testing rates will be monitored to confirm if this unexpected benefit is sustained.