title: Recalibration of blood analytes over 25 years in the atherosclerosis risk in communities study: impact of recalibration on chronic kidney disease prevalence and incidence.
abstract: BACKGROUND
  Equivalence of laboratory tests over time is important for longitudinal studies. Even a small systematic difference (bias) can result in substantial misclassification.
  
  
  METHODS
  We selected 200 Atherosclerosis Risk in Communities Study participants attending all 5 study visits over 25 years. Eight analytes were remeasured in 2011-2013 from stored blood samples from multiple visits: creatinine, uric acid, glucose, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, and high-sensitivity C-reactive protein. Original values were recalibrated to remeasured values with Deming regression. Differences >10% were considered to reflect substantial bias, and correction equations were applied to affected analytes in the total study population. We examined trends in chronic kidney disease (CKD) pre- and postrecalibration.
  
  
  RESULTS
  Repeat measures were highly correlated with original values [Pearson r > 0.85 after removing outliers (median 4.5% of paired measurements)], but 2 of 8 analytes (creatinine and uric acid) had differences >10%. Original values of creatinine and uric acid were recalibrated to current values with correction equations. CKD prevalence differed substantially after recalibration of creatinine (visits 1, 2, 4, and 5 prerecalibration: 21.7%, 36.1%, 3.5%, and 29.4%, respectively; postrecalibration: 1.3%, 2.2%, 6.4%, and 29.4%). For HDL cholesterol, the current direct enzymatic method differed substantially from magnesium dextran precipitation used during visits 1-4.
  
  
  CONCLUSIONS
  Analytes remeasured in samples stored for approximately 25 years were highly correlated with original values, but 2 of the 8 analytes showed substantial bias at multiple visits. Laboratory recalibration improved reproducibility of test results across visits and resulted in substantial differences in CKD prevalence. We demonstrate the importance of consistent recalibration of laboratory assays in a cohort study.
authors.affiliation: Department of Epidemiology and the Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD;
authors.forename: Christina M
authors.initials: CM
authors.lastname: Parrinello
authors.affiliation: Department of Epidemiology and the Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; Division of Nephrology and.
authors.forename: Morgan E
authors.initials: ME
authors.lastname: Grams
authors.affiliation: Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC;
authors.forename: David
authors.initials: D
authors.lastname: Couper
authors.affiliation: Division of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, Houston, TX;
authors.forename: Christie M
authors.initials: CM
authors.lastname: Ballantyne
authors.affiliation: Division of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, Houston, TX;
authors.forename: Ron C
authors.initials: RC
authors.lastname: Hoogeveen
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN.
authors.forename: John H
authors.initials: JH
authors.lastname: Eckfeldt
authors.affiliation: Department of Epidemiology and the Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; Division of General Internal Medicine, Department of Medicine, Johns Hopkins University, Baltimore, MD;
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Selvin
authors.affiliation: Department of Epidemiology and the Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; Division of General Internal Medicine, Department of Medicine, Johns Hopkins University, Baltimore, MD; coresh@jhu.edu.
authors.forename: Josef
authors.initials: J
authors.lastname: Coresh
mesh_terms: D000368:Aged; D050197:Atherosclerosis / Q000097:blood*; D001774:Blood Chemical Analysis / Q000379:methods*; D001800:Blood Specimen Collection / Q000379:methods*; D002138:Calibration; D008076:Cholesterol, HDL / Q000097:blood; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000453:epidemiology*; D015203:Reproducibility of Results; D015983:Selection Bias; D013997:Time Factors; D014481:United States / Q000453:epidemiology
chemical_list: D008076:Cholesterol, HDL