Progress of HIV care cascade and transition dynamics along the continuum of care among persons living with HIV in Ifakara, Tanzania: a prospective study

While cross-sectional assessments offer snapshots of care cascade progress, longitudinal analyses are essential to capture the dynamic engagement in care of people living with HIV (PLHIV). We assessed the advancement of the HIV cascade, engagement in care and factors associated with different transitions among PLHIV at the Chronic Disease Clinic of Ifakara, Ifakara, Tanzania, using both cross-sectional and longitudinal analyses. In this prospective study, we included PLHIV enrolled in care from 04/2005 to 09/2022 and consented to participate in the Kilombero and Ulanga Antiretroviral Cohort. A cross-sectional care cascade was assessed descriptively. In longitudinal analysis, we used continuous-time, non-parametric multistate, and Cox proportional hazards models to assess engagement in care and factors associated with different transitions, respectively. Of the 11,591 PLHIV enrolled, 7,353 (63%) were female and 8,637 (75%) were adults aged 20–49 years. Cross-sectionally, 3,647 participants initiated on antiretroviral therapy (ART) were retained in care, and of these, 3,450 (95%) had a viral load < 1000 copies/mL as of September 2022. The repeated cross-sectional cascade showed the proportion of ART initiation increased over time (from 67% in the period 04/2005-01/2009 to 96% in 04/2019-09/2022). In longitudinal assessment, at 12 months, 45% were in care, and 24% were lost to follow-up (LTFU). After being LTFU, 34% returned to care within 12 months. Being on ART at baseline was associated with a reduced risk of LTFU (Hazard ratio [HR] = 0.71; 95% Confidence interval [CI]: 0.67–0.75) and an increased hazard of return to care after being LTFU (HR = 1.38; 95% CI: 1.31–1.45). PLHIV aged ≥ 15 years and being in WHO stage 3 (HR = 1.09; 95% CI: 1.03–1.16) and stage 4 (HR = 1.31; 95% CI: 1.21–1.42) were associated with an elevated risk of LTFU, while WHO stage 4 (HR = 0.76; 95% CI: 0.69–0.83) was associated with a reduced hazard of returning to care after being LTFU. Cross-sectional analyses showed a high proportion of viral load suppression, achieving the UNAIDS target among PLHIV retained in care. However, longitudinal models revealed that many PLHIV transitioned in-and-out of care. The first 12 months after enrolment and LTFU are critical periods that should be targeted for maximizing retention. Not applicable.