Reevaluating late HIV diagnosis incorporating recent infection evidence: a population-based study in Southwest China (2020–2023)

BACKGROUND: Despite global advances in HIV treatment and prevention, the proportion of patients with late HIV diagnosis remains persistently high. The CD4-based definition of late HIV diagnosis has limitations during early seroconversion when the CD4 count may transiently decrease, leading to misclassification and overestimation. This study integrated evidence of recent infection from HIV testing history to redefine late HIV diagnosis, quantify the extent of overestimation, and identify factors associated with reclassification. METHODS: We conducted a population-based study on newly reported people living with HIV from 2020 to 2023 in a prefecture-level city in Southwest China. Data were obtained from the Comprehensive Response Information Management System and matched with the Universal Health Information System. People initially classified as late (CD4 count < 350 cells/µL or an AIDS-defining event) were reclassified as non-late if they had a documented negative HIV test within 12 months before diagnosis. The proportion of patients with a late HIV diagnosis was recalculated after reclassification. Multivariate logistic regression was used to identify factors associated with reclassification. RESULTS: Among 5,481 newly reported people living with HIV, 2,228 (40.65%) had a documented previous negative HIV test. After reclassification, the proportion of patients with late HIV diagnosis decreased from 62.89% (3,447/5,481) to 53.68% (2,942/5,481). Older individuals presented a higher correction rate (19.56%). Among the subgroup of people with a previous negative HIV testing history, the proportion decreased from 61.62% (1,373/2,228) to 38.96% (868/2,228). Multivariable analysis revealed that, compared to individuals aged < 50 years, those aged ≥ 60 years were significantly more likely to be reclassified (aOR: 1.426, 95% CI: 1.008-2.017). CONCLUSIONS: Relying solely on the CD4-based definition overestimates the prevalence of late HIV diagnosis, particularly among older adults. Incorporating evidence of recent infection into the definition can improve the accuracy of late HIV diagnosis assessments. However, individuals presenting with low CD4 count during recent infection remain highly vulnerable and require immediate antiretroviral therapy.