Sensitivity requirements for the point of care diagnosis of Chlamydia trachomatis and Neisseria gonorrhoeae in women

Background/objectives: Most current tests for Neisseria gonorrhoeae and Chlmydia trachomatis require the support of a laboratory, and results are not usually available before the patient has left the clinic. This delay can lead to patients not returning for treatment and may allow further STI transmission to occur. Current rapid point of care (POC) STI tests and the syndromic approach are less sensitive than gold standard tests, but allow treatment at the initial visit. This study estimates the required sensitivity of POC tests that ensures as many STIs are averted as with current gold standard tests. Methods: A mathematical model is developed to compare the STIs averted using different STI diagnostic methods. Data from Benin, South Africa, Tanzania, and England are used to explore how the required sensitivity differs between settings. Results: The required sensitivity of a POC test is low if there is significant STI transmission during the delay in treatment for the gold standard test and/or few women return for treatment. For example, the required sensitivity of a POC test for C trachomatis is 50% ( gold standard test sensitivity is 90%) if either 55% return for treatment and there is no STI transmission, or 80% return for treatment and 50% of infected women infect their partner during the delay in treatment. Furthermore, in these settings a POC test of moderate sensitivity can lead to significantly more STI averted than the gold standard test. Conclusions: These results support the use of moderate sensitivity POC tests in scenarios where many women will not return for treatment, and in populations where the delay in treatment would result in significant STI transmission.