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

Abstract

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.

Figure 1

Cascade adapted from: Marks G, Gardner LI, Craw J, Crepaz N. Entry and retention in medical care among HIV-diagnosed persons: a meta-analysis. AIDS. 2010; 24:2665-2678 and Centers for Disease Control and Prevention. Vital signs: HIV prevention through care and treatment—United States. MMWR. 2011; 60:1618-1623. Linkage to care metrics examined are listed in the table and are based on clinic visits or laboratory tests. Visits refer to clinic visits for HIV care; i.e., an outpatient visit with a provider with prescribing privileges in an HIV care setting. Either a CD4 T-cell count or HIV-1 RNA level was considered a laboratory test. Laboratory tests drawn on the same day were counted as one test. The date of the laboratory test was the date that the laboratory test was drawn, regardless of when it was entered into the database. Retention in care was defined as two clinic visits spaced 90 days apart between 366 and 730 days after diagnosis. Virologic suppression was defined as a HIV-1 RNA level <200 copies/ml, between 366 and 730 days after diagnosis.