The VACS Index Predicts Mortality in a Young, Healthy HIV Population Starting Highly Active Antiretroviral Therapy

• Type of Material: Article
• Authors: Ionut Bebu, Uniformed Services University; Janet Tate, Yale University; David Rimland, Emory University; Octavio Mesner, Uniformed Services University; Grace E. Macalino, Uniformed Services University; Anuradha Ganesan, Uniformed Services University; Jason F. Okulicz, Uniformed Services University; Mary Bavaro, Uniformed Services University; Amy C. Weintrob, Uniformed Services University; Amy C. Justice, Yale University; Brian K. Agan, Uniformed Services University
• Language: English
• Date: 2014-02-01
• Publisher: Lippincott, Williams & Wilkins
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: Copyright © 2013 by Lippincott Williams and Wilkins.
• Final Published Version (URL): http://dx.doi.org/10.1097/QAI.0000000000000045
• Title of Journal or Parent Work: Journal of Acquired Immune Deficiency Syndromes
• ISSN: 1525-4135
• Volume: 65
• Issue: 2
• Start Page: 226
• End Page: 230
• Grant/Funding Information: Support for this work (IDCRP-000) was provided by the Infectious Disease Clinical Research Program (IDCRP), a Department of Defense (DoD) program executed through the Uniformed Services University of the Health Sciences.; This project has been funded in whole, or in part, with federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health (NIH), under Inter-Agency Agreement Y1-AI-5072.
• Keywords: military; Life Sciences & Biomedicine; Immunology; HIV; early diagnosis; Science & Technology; CARE; VACS index; Infectious Diseases; validation
• Research Categories: Health Sciences, Medicine and Surgery; Biology, Virology

Abstract

Background: The Veterans Aging Cohort Study (VACS) index is a weighted combination of age and 8 clinical variables. It has been well correlated with all-cause mortality among HIV-infected patients. The US Military HIV Natural History Study (NHS) cohort provides a different validation population profile, being younger and healthier. A significant portion of the US HIV population is similarly composed; so, evaluation of the VACS index in this population is of great interest. Methods: NHS subjects have medical history and laboratory data collected at 6-month visits. We performed an external validation of the VACS index in the NHS evaluating correlation, discrimination, and calibration for all-cause mortality after highly active antiretroviral therapy initiation (HI). We then tested whether combining longitudinal VACS index values at different time points improves prediction of mortality. Results: The VACS index at 1 year after HI was well correlated with all-cause mortality (Harrell c statistic 0.78), provided good discrimination (log-rank P < 0.05), and was marginally well calibrated using Brier score. Accounting for VACS index at HI and 6 months after HI significantly improved a standard model, including only the VACS index at 1 year after HI (net reclassification improvement = 25.2%, 95% CI: 10.9% to 48.9%). Conclusions: The VACS index was well correlated and provided good discrimination with respect to all-cause mortality among highly active antiretroviral therapy initiating subjects in the NHS. Moderate overprediction of mortality in this young, healthy population suggests minor recalibration that could improve fit among similar patients. Considering VACS index at HI and 6 months improved outcome prediction and allowed earlier risk assessment.