Accuracy of definitions for linkage to care in persons living with HIV

Objective: To compare the accuracy of linkage to care metrics for patients diagnosed with HIV using retention in care and virological suppression as the gold standards of effective linkage. Design: A retrospective cohort study of patients aged 18 years and older with newly diagnosed HIV infection in the City of Philadelphia, 2007-2008. Methods: Times from diagnosis to clinic visits or laboratory testing were used as linkage measures. Outcome variables included being retained in care and achieving virological suppression, 366-730 days after diagnosis. Positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) for each linkage measure and retention, and virological suppression outcomes are described. Results: Of the 1781 patients in the study, 503 (28.2%) were retained in care in the Ryan White system and 418 (23.5%) achieved virological suppression 366-730 days after diagnosis. The linkage measure with the highest PPV for retention was having 2 clinic visits within 365 days of diagnosis, separated by 90 days (74.2%). Having a clinic visit between 21 and 365 days after diagnosis had both the highest NPV for retention (94.5%) and the highest adjusted AUC for retention (0.872). Having 2 tests within 365 days of diagnosis, separated by 90 days, had the highest adjusted AUC for virological suppression (0.780). Conclusions: Linkage measures associated with clinic visits had higher PPV and NPV for retention, whereas linkage measures associated with laboratory testing had higher PPV and NPV for retention. Linkage measures should be chosen based on the outcome of interest.