[Characteristics of CD4+T lymphocyte counts changed in antiretroviral-naive and antiretroviral-treated HIV-infected individuals' cohorts in Tianjin].

Objective: To characterize the dynamic changes in CD4+T lymphocyte (CD4) counts among HIV-infected individuals in Tianjin, China, under untreated and antiretroviral treatment (ART) conditions, and to provide evidence for optimizing HIV case management and prevention strategies. Methods: The data were derived from the follow-up records of HIV-infected individuals aged 15 and above in Tianjin from 2005 to 2024, obtained from the Chinese Disease Control and Prevention Information System. Records were split into non-ART and ART phases as time-dependent cohorts, with the same HIV-infected individuals contributing to both phases before and after treatment initiation. A continuous-time Markov model was applied to both cohorts to estimate annual transition rates of CD4 counts across immunological categories. In addition, a linear mixed-effects model with natural splines was fitted to the ART cohort to characterize individual recovery trajectories stratified by baseline CD4 count levels. Results: The non-ART cohort and the ART cohort enrolled 709 and 2 865 HIV-infected individuals, respectively. In untreated individuals, CD4 counts declined progressively: annual transition rates from ≥500 to 350-499, 350-499 to 200-349, and 200-349 to <200 cells/μl were 34.8% (95%CI: 30.3%-39.9%), 19.0% (95%CI: 16.1%-22.5%), and 9.3% (95%CI: 6.8%-12.7%), with mean sojourn times of 2.87, 5.25, and 10.73 years, respectively. After ART initiation, CD4 counts recovery followed a nonlinear pattern: transition rates from <200 to 200-349, 200-349 to 350-499, and 350-499 to ≥500 cells/μl were 91.8% (95%CI: 86.6%-97.4%), 63.7% (95%CI: 60.9%-66.6%), and 42.6% (95%CI: 40.9%-44.4%), with corresponding mean sojourn times of 1.09, 1.57, and 2.35 years. Conclusions: CD4 count transition rates in non-ART HIV-infected individuals decreased as immunodeficiency progressed, while post-ART recovery rates varied substantially across CD4 count strata.