The World Health Organization (WHO) adult HIV diagnostic testing strategy requires up to 4-7 rapid diagnostic tests (RDTs) prior to ART initiation. Although more expensive than RDTs, adding POC NAT to current testing strategies may minimize misdiagnoses and attrition, permitting ART initiation with fewer tests.
Using the Cost-Effectiveness of Preventing AIDS Complications model, we simulated a one-time HIV test in addition to status quo (SQ) testing practices in a low HIV-undiagnosed prevalence setting (1.3%): Côte d’Ivoire (CI). Model inputs included mean age (37y), SQ HIV testing (74 tests/1,000PY), and costs of ART ($6-22/m), HIV care ($27-38/m), and assays (RDT $1.50; POC NAT $27.92). We assessed 3 testing strategies: RDT-based strategies recommended by the WHO (RDT-WHO) and CI (RDT-CI), and a novel strategy: POC NAT to resolve RDT discordancy (NAT-Resolve). We calculated the number of true/false negative/positive (TN, TP, FN, FP) results for each strategy. We modeled 3 scenarios: A) sensitivity/specificity from WHO prequalification reports and no attrition between tests, B) sensitivity/specificity from WHO prequalification reports and reported attrition and result-delay rates, and C) field-based RDT sensitivity/specificity and reported attrition and result-delay rates. We reported life expectancy (LE) and costs per misdiagnosis and per person in the tested population, as well as incremental cost-effectiveness ratios (ICERs, in $/year-of-life saved [YLS]; threshold ≤$1,720 [CI per-capita GDP]).
Relative to the tested population, there were few misdiagnoses in Scenarios A and B (Table 1). A FN diagnosis led to a LE loss of 5y (vs. a TP); this LE loss was most sensitive to HIV detection rates after developing an opportunistic infection. A FP diagnosis increased costs by $6,500 (vs. a TN); this cost increase was most sensitive to costs of HIV care and ART, and time spent misdiagnosed. In Scenarios A and B, for the entire tested population, LE and costs were very similar between all 3 strategies. In Scenario C, with field-based RDT characteristics and attrition, NAT-Resolve averted more misdiagnoses and was cost-saving compared to RDT-WHO and RDT-CI.
With HIV Rapid Diagnostic Testing-based strategies, the impacts of misdiagnoses may be substantial. In combination with RDTs, in practice in a low HIV prevalence setting, POC NAT-based testing strategies will minimize misdiagnoses, improve attrition, and be cost-saving.