Lateral flow assay-based CD4 cell count testing for advanced HIV disease.

The global policy shift to treating all people living with HIV, regardless of CD4 cell count, has inadvertently led donors and national programmes to reduce their investments in CD4 testing. The subsequent decline in testing volumes has caused manufacturers to discontinue major point-of-care CD4 testing instruments, despite these tests being crucial for the diagnosis of advanced HIV disease (AHD). Mortality from AHD remains high, with an estimated 630 000 deaths among people living with HIV in 2023. CD4 lateral flow assay (LFA) testing could provide pragmatic screening for AHD. Published studies show moderate-to-high diagnostic performance of Visitect CD4 LFA tests in venous blood samples, with a sensitivity of 93·4-95·0% and specificity of 81·9-87·7%, but the specificity from fingerprick samples is substantially lower (61·4-78·3%). Therefore, the interplay between diagnostic test performance, other attributes (eg, result turnaround time, accessibility, feasibility of decentralisation, cost-effectiveness, and diagnostic yield), and AHD prevalence needs to be considered. Given its potential to cost-effectively support and increase AHD screening, and to subsequently assist in long-term reductions in HIV mortality beyond 2030 UNAIDS targets, a greater appreciation of the diagnostic yield of LFA-based CD4 testing is crucial. Implementation science and policy development should consider public health impacts in addition to test clinical accuracy.