title: HIV viremia and T-cell activation differentially affect the performance of glomerular filtration rate equations based on creatinine and cystatin C.
abstract: BACKGROUND
  Serum creatinine and cystatin C are used as markers of glomerular filtration rate (GFR). The performance of these GFR markers relative to exogenously measured GFR (mGFR) in HIV-positive individuals is not well established.
  
  
  METHODS
  We assessed the performance of the chronic kidney disease epidemiology collaboration equations based on serum concentrations of creatinine (eGFRcr), cystatin C (eGFRcys) and both biomarkers combined (eGFRcr-cys) in 187 HIV-positive and 98 HIV-negative participants. Measured GFR was calculated by plasma iohexol clearance. Bias and accuracy were defined as the difference between eGFR and mGFR and the percentage of eGFR observations within 30% of mGFR, respectively. Activated CD4 and CD8 T-cells (CD38+ HLA-DR+) were measured by flow cytometry.
  
  
  RESULTS
  The median mGFR was >100 ml/min/1.73 m(2) in both groups. All equations tended to be less accurate in HIV-positive than in HIV-negative subjects, with eGFRcr-cys being the most accurate overall. In the HIV-positive group, eGFRcys was significantly less accurate and more biased than eGFRcr and eGFRcr_cys. Additionally eGFRcys bias and accuracy were strongly associated with use of antiretroviral therapy, HIV RNA suppression, and percentages of activated CD4 or CD8 T-cells. Hepatitis C seropositivity was associated with larger eGFRcys bias in both HIV-positive and HIV-negative groups. In contrast, eGFRcr accuracy and bias were not associated with HIV-related factors, T-cell activation, or hepatitis C.
  
  
  CONCLUSIONS
  The performance of eGFRcys relative to mGFR was strongly correlated with HIV treatment factors and markers of T-cell activation, which may limit its usefulness as a GFR marker in this population.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Bhavna
authors.initials: B
authors.lastname: Bhasin
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America ; Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Bryan
authors.initials: B
authors.lastname: Lau
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Mohamed G
authors.initials: MG
authors.lastname: Atta
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Derek M
authors.initials: DM
authors.lastname: Fine
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Estrella
authors.affiliation: Department of Pediatrics, University of Rochester School of Medicine, Rochester, New York, United States of America.
authors.forename: George J
authors.initials: GJ
authors.lastname: Schwartz
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Lucas
mesh_terms: D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D015658:HIV Infections / Q000097:blood / Q000276:immunology* / Q000503:physiopathology; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000453:epidemiology / Q000276:immunology / Q000503:physiopathology; D014766:Viremia / Q000097:blood / Q000276:immunology* / Q000503:physiopathology
chemical_list: D055316:Cystatin C; D003404:Creatinine