title: Identification of incident CKD stage 3 in research studies.
abstract: BACKGROUND
  In epidemiologic research, incident chronic kidney disease (CKD) commonly is determined by laboratory tests performed at planned study visits. Given the morbidity and mortality associated with CKD, persons with incident disease may be less likely to attend scheduled visits, affecting observed associations. The objective of this study was to quantify loss to follow-up by CKD status and determine whether supplementation with diagnostic code data improves capture of incident CKD.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  11,560 participants in the Atherosclerosis Risk in Communities (ARIC) Study underwent continuous surveillance for hospitalizations and death from baseline visit (1996-1999) to follow-up visit (2011-2013). A subset of hospitalizations in Washington County, MD, was used in diagnostic code validation (n=2,540).
  
  
  METHODS
  Baseline demographics and comorbid conditions.
  
  
  RESULTS
  Incident CKD stage 3 ascertained by follow-up visit (visit-based definition) or hospitalization surveillance (hospitalization-based definition).
  
  
  METHODS
  Visit-based definition: ≥25% decline from baseline estimated glomerular filtration rate to <60 mL/min/1.73 m2 at follow-up visit; hospitalization-based definition: hospitalization CKD diagnostic code.
  
  
  RESULTS
  Of 11,560 participants, 5,951 attended the follow-up visit and 9,264 were hospitalized. Never-hospitalized participants were younger, more often female, and had fewer comorbid conditions; 73.5% attended the follow-up visit. Incident CKD stage 3 occurred in 1,172 participants by the visit-based definition (251 were never hospitalized) and 1,078 participants by the hospitalization-based definition (237 attended the follow-up study visit). Sensitivity of the hospitalization-based CKD definition was 35.5% (95% CI, 31.6%-39.7%); specificity was 95.7% (95% CI, 94.2%-96.8%). Sensitivity was higher with later time period, older participant age, and baseline prevalent diabetes and CKD.
  
  
  CONCLUSIONS
  A subset of hospitalizations was used for validation; 15-year gap between study visits.
  
  
  CONCLUSIONS
  The sensitivity of diagnostic code-identified CKD is low and varies by certain factors; however, supplementing a visit-based definition with hospitalization information can increase disease identification during periods of follow-up without study visits.
authors.affiliation: Division of Nephrology, Department of Medicine, Johns Hopkins University, Baltimore, MD. Electronic address: mgrams2@jhmi.edu.
authors.forename: Morgan E
authors.initials: ME
authors.lastname: Grams
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
authors.forename: Casey M
authors.initials: CM
authors.lastname: Rebholz
authors.affiliation: Division of Nephrology, Department of Medicine, Johns Hopkins University, Baltimore, MD.
authors.forename: Blaithin
authors.initials: B
authors.lastname: McMahon
authors.affiliation: Division of Nephrology, Department of Medicine, Johns Hopkins University, Baltimore, MD.
authors.forename: Seamus
authors.initials: S
authors.lastname: Whelton
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
authors.forename: Shoshana H
authors.initials: SH
authors.lastname: Ballew
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Selvin
authors.affiliation: Department of Biostatistics, University of North Carolina, Chapel Hill, NC.
authors.forename: Lisa
authors.initials: L
authors.lastname: Wruck
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; Division of General Internal Medicine, Department of Medicine, Johns Hopkins University, Baltimore, MD.
authors.forename: Josef
authors.initials: J
authors.lastname: Coresh
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate / Q000502:physiology; D006760:Hospitalization / Q000639:trends; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance / Q000379:methods; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000175:diagnosis* / Q000503:physiopathology
keywords: CKD surveillance; Chronic kidney disease (CKD); administrative data; diagnostic codes; identification; incident; loss to follow-up; screening; validation
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