title: Impact of defined clinical population and missing data on temporal trends in HIV viral load estimation within a health care system.
abstract: OBJECTIVE
  Community viral load (CVL) estimates vary based on analytic methods. We extended the CVL concept and used data from the Veterans Health Administration (VA) to determine trends in the health care system viral load (HSVL) and its sensitivity to varying definitions of the clinical population and assumptions regarding missing data.
  
  
  METHODS
  We included HIV-infected patients in the Veterans Aging Cohort Study, 2000-2010, with at least one documented CD4 count, HIV-1 RNA or antiretroviral prescription (n = 37 318). We created 6-month intervals including patients with at least one visit in the past 2 years. We assessed temporal trends in clinical population size, patient clinical status and mean HSVL and explored the impact of varying definitions of the clinical population and assumptions about missing viral load.
  
  
  RESULTS
  The clinical population size varied by definition, increasing from 16 000-19 000 patients in 2000 to 23 000-26 000 in 2010. The proportion of patients with suppressed HIV-1 RNA increased over time. Over 20% of patients had no viral load measured in a given interval or the past 2 years. Among patients with a current HIV-1 RNA, mean HSVL decreased from 97 800 HIV-1 RNA copies/mL in 2000 to 2000 copies/mL in 2010. When current HIV-1 RNA data were unavailable and the HSVL was recalculated using the last available HIV-1 RNA, HSVL decreased from 322 300 to 9900 copies/mL. HSVL was underestimated when using only current data in each interval.
  
  
  CONCLUSIONS
  The CVL concept can be applied to a health care system, providing a measure of health care quality. Like CVL, HSVL estimates depend on definitions of the clinical population and assumptions about missing data.
authors: Yale University School of Medicine, New Haven, CT, USA.|Center for Interdisciplinary Research on AIDS, Yale University School of Public Health, New Haven, CT, USA.
authors: E J
authors: EJ
authors: Edelman
authors: Yale University School of Medicine, New Haven, CT, USA.|VA Connecticut Healthcare System, West Haven, CT, USA.
authors: J P
authors: JP
authors: Tate
authors: Yale University School of Medicine, New Haven, CT, USA.|Center for Interdisciplinary Research on AIDS, Yale University School of Public Health, New Haven, CT, USA.
authors: D A
authors: DA
authors: Fiellin
authors: James J. Peters VA Medical Center, Bronx, NY, USA.|The Icahn School of Medicine at Mt. Sinai, New York, NY, USA.
authors: S T
authors: ST
authors: Brown
authors: National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, USA.
authors: K
authors: K
authors: Bryant
authors: Emory Rollins School of Public Health, Altanta, GA, USA.|Emory University School of Medicine, Atlanta, GA, USA.
authors: N
authors: N
authors: Gandhi
authors: Washington DC VA Medical Center and George Washington University School of Medicine, Washington, DC, USA.
authors: C L
authors: CL
authors: Gibert
authors: VA Greater Los Angeles Healthcare System and David Geffen School of Medicine, Los Angeles, CA, USA.
authors: M B
authors: MB
authors: Goetz
authors: VA Connecticut Healthcare System, West Haven, CT, USA.
authors: K S
authors: KS
authors: Gordon
authors: Michael E. DeBakey Veterans Affairs Medical Center and Baylor College of Medicine, Houston, TX, USA.
authors: M C
authors: MC
authors: Rodriguez-Barradas
authors: New York University School of Medicine, New York, NY, USA.
authors: R S
authors: RS
authors: Braithwaite
authors: Emory University School of Medicine, Atlanta, GA, USA.|Atlanta Veterans Affairs Medical Center, Decatur, GA, USA.
authors: D
authors: D
authors: Rimland
authors: Yale University School of Medicine, New Haven, CT, USA.|Center for Interdisciplinary Research on AIDS, Yale University School of Public Health, New Haven, CT, USA.|VA Connecticut Healthcare System, West Haven, CT, USA.
authors: A C
authors: AC
authors: Justice
mesh_terms: D000328:Adult; D018791:CD4 Lymphocyte Count; D015331:Cohort Studies; D005260:Female; D015658:HIV Infections / Q000175:diagnosis* / Q000821:virology; D015497:HIV-1; D006801:Humans; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance / Q000379:methods*; D012367:RNA, Viral / Q000032:analysis; D014728:Veterans; D019562:Viral Load
chemical_list: D012367:RNA, Viral
keywords: HIV; community viral load; epidemiological methods; population surveillance; quality of health care