Estimating Retention in HIV Care Accounting for Patient Transfers: A National Laboratory Cohort Study in South Africa

CD4 cells are a type of white blood cell that protect the body from infections. HIV targets and destroys CD4 cells, and the medical community has long used an HIV-infected person’s CD4 count to determine the severity of their disease and their eligibility to receive antiretroviral therapy (ART).

In 2015, the World Health Organization (WHO) recommended removing CD4 count thresholds for HIV treatment eligibility based on clinical trial evidence showing ART’s benefits to patients and ability to reduce transmission to uninfected partners. The aim of the WHO recommendation was to increase the number of patients on ART and reduce new infections. However, the WHO specifically noted that the expected gains of the recommendation could only be achieved if improvements were made in retaining patients once they began ART.

To date, estimates of retention worldwide in HIV treatment programs have varied widely. Most analyses have been from the perspective of individual cohorts where researchers do not have the ability to trace patients who move from one HIV treatment site to another, something that may be common.

In a new journal article published in PLOS Medicine, Jacob Bor and colleagues assess ART retention in South Africa, a country with a national provider of laboratory investigations that has maintained results on most patients in South Africa since the beginning of the treatment program in 2004. They use probabilistic matching techniques to turn these data into a longitudinal cohort that can be used to determine when patients were lost to follow-up and when they moved between clinics. This approach allowed the authors to compare retention in care from the perspective of the clinic (the perspective most often reported) and from the national perspective, which accounts for movement between sites.

Main findings:

• From the clinic perspective, 29.1 percent of patients who started HIV treatment according to national guidelines between 2004 and 2006 were still in care six years later.

• However, when looking from a national perspective which accounted for movement between clinics, retention was estimated to be 63.3 percent at six years.

These findings suggest that there is substantial movement among patients between HIV clinics in South Africa, and that ignoring these movements has the potential to strongly underestimate retention in HIV care. The results are encouraging as they suggest patients who left care after starting treatment early in the epidemic often returned to care at later points in time. The authors note that further research is needed to understand the care trajectories and long-run health outcomes of patients who cycle into and out of care at multiple facilities.