Abstract
Although patient attrition is recognized as a threat to the long-term success of antiretroviral therapy programs worldwide, there is no universal definition for classifying patients as lost to follow-up (LTFU). We analyzed data from health facilities across Africa, Asia, and Latin America to empirically determine a standard LTFU definition. At a set "status classification" date, patients were categorized as either "active" or "LTFU" according to different intervals from time of last clinic encounter. For each threshold, we looked forward 365 d to assess the performance and accuracy of this initial classification. The best-performing definition for LTFU had the lowest proportion of patients misclassified as active or LTFU. Observational data from 111 health facilities-representing 180,718 patients from 19 countries-were included in this study. In the primary analysis, for which data from all facilities were pooled, an interval of 180 d (95% confidence interval [CI]: 173-181 d) since last patient encounter resulted in the fewest misclassifications (7.7%, 95% CI: 7.6%-7.8%). A secondary analysis that gave equal weight to cohorts and to regions generated a similar result (175 d); however, an alternate approach that used inverse weighting for cohorts based on variance and equal weighting for regions produced a slightly lower summary measure (150 d). When examined at the facility level, the best-performing definition varied from 58 to 383 d (mean=150 d), but when a standard definition of 180 d was applied to each facility, only slight increases in misclassification (mean=1.2%, 95% CI: 1.0%-1.5%) were observed. Using this definition, the proportion of patients classified as LTFU by facility ranged from 3.1% to 45.1% (mean=19.9%, 95% CI: 19.1%-21.7%). Based on this evaluation, we recommend the adoption of ≥180 d since the last clinic visit as a standard LTFU definition. Such standardization is an important step to understanding the reasons that underlie patient attrition and establishing more reliable and comparable program evaluation worldwide. Please see later in the article for the Editors' Summary.
Highlights
Unprecedented gains have been made in the expansion of services for antiretroviral therapy (ART) in resource-constrained settings
A systematic review of sub-Saharan African cohorts reported lost to follow-up (LTFU) rates as high as 35% in the 3 y following ART initiation [3,4], a finding supported by other regional reports [5,6,7]
Applied to a cohort of 33,704 ART patients in Lusaka, Zambia [9,10], we found that a threshold of $56 d since last missed visit led to the fewest misclassifications of a patient’s status as active or LTFU (5.1%, 95% confidence interval [CI]: 4.8%–5.3%)
Summary
Unprecedented gains have been made in the expansion of services for antiretroviral therapy (ART) in resource-constrained settings. Patient attrition and losses to followup, have emerged as legitimate threats to the long-term success of these programs. An interval that is close to the visit date, for example, may be highly sensitive (i.e., a high proportion of patients are accurately identified as LTFU), but specificity will be low. An interval that is long will be highly specific (i.e., a high proportion of patients are accurately classified as active), but sensitivity may be limited. Patient attrition is recognized as a threat to the long-term success of antiretroviral therapy programs worldwide, there is no universal definition for classifying patients as lost to follow-up (LTFU). For people living in developed countries, HIV infection became a chronic condition. For people living in developing countries, ART was prohibitively expensive, and HIV/AIDS remained a fatal illness. By the end of 2009, more than a third of people living in these countries who needed ART were receiving it
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