ABSTRACT
OBJECTIVES: This service improvement study scoped the value of using quantitative reactivity levels (RL) to introduce a two-tier counselling approach in HIV self-sampling services. The objectives were to (1) use self-reported confirmatory test results to estimate the positive predictive value (PPV) of the first-line assay and (2) to calculate the impact on the PPV and theoretical negative predictive value of a range of proposed RL thresholds, which could be used to differentiate between higher and lower reactive results. METHODS: We studied HIV testing data from a UK-based online sexual health service from 1 December 2018 to 15 July 2020. Routinely collected, anonymised data on RL and self-reported confirmatory testing outcomes were used to calculate PPV at a range of RL thresholds. RESULTS: 116 474 adequate HIV tests were reported during the study period, of which 889 were reactive (0.76%, 95% CI 0.71% to 0.82%). Confirmatory testing outcomes were self-reported by 572 (64.34%) reactive service users, of whom 43 (7.52%) had a new HIV diagnosis, 412 (72.03%) were negative and 117 (20.45%) already had a known HIV diagnosis. PPV was 9.45% at an RL threshold of >1. Quantitative RLs were reported for 30 281 results, of which 200 were reactive. PPV increased to 80% at an RL threshold of >30. No confirmed HIV diagnoses were reported among service users with RL <30. CONCLUSION: RLs could be used to support a more nuanced approach to counselling, potentially reducing anxiety prior to confirmatory testing.
