Global Health

July 15, 2013

Defining patient retention

Vanderbilt researchers propose guidelines for defining patient retention in clinical studies – an important parameter that affects study conclusions and program evaluations.


The way that researchers define patient retention in a clinical study – “loss to follow-up” (LTFU) – can significantly impact study results, investigators in Vanderbilt’s Department of Biostatistics and Institute for Global Health have found. Retaining patients (reducing LTFU) with chronic diseases is essential for optimizing outcomes and, in the case of HIV infection, limiting the spread of disease.

Using data from a cohort of HIV-infected patients starting antiretroviral therapy in Mozambique, Bryan Shepherd, Ph.D., Meridith Blevins, M.S., and colleagues studied the impact of different LTFU definitions found in the HIV literature on estimates of LTFU, AIDS and death. They report in the American Journal of Epidemiology that estimates of LTFU at 2 years ranged from 22 to 84 percent, depending on the definition used.

The investigators conclude that the choice of definition can greatly affect study conclusions and program evaluations. They suggest general guidelines for selecting LTFU definitions – guidelines that are broadly applicable to any observational study of chronic diseases.

This research was supported by the President’s Emergency Plan for AIDS Relief (PEPFAR) through the Centers for Disease Control and Prevention and by a grant from the National Institutes of Health (AI093234).