title: A Risk Score to Guide Cystatin C Testing to Detect Occult-Reduced Estimated Glomerular Filtration Rate.
abstract: OBJECTIVE
  Persons with occult-reduced estimated glomerular filtration rate (eGFR<60 ml/min/1.73 m2 detected by serum cystatin C but missed by creatinine) have high risk for complications. Among persons with preserved kidney function by creatinine-based eGFR (eGFRcreat>60 ml/min/1.73 m2), tools to guide cystatin C testing are needed.
  
  
  METHODS
  We developed a risk score to estimate an individual's probability of reduced eGFR by cystatin C (eGFRcys<60 ml/min/1.73 m2) in The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study and externally validated in the Third National Health and Nutrition Examination Survey (NHANES III). We used logistic regression with Bayesian model averaging and variables available in practice. We assessed performance characteristics using calibration and discrimination measures.
  
  
  RESULTS
  Among 24,877 adults with preserved kidney function by creatinine, 13.5% had reduced eGFRcys. Older and Black participants, current smokers and those with higher body mass index, lower eGFRcreat, diabetes, hypertension and history of cardiovascular disease were more likely to have occult-reduced eGFR (p<0.001). The final risk function had a c-statistic of 0.87 in REGARDS and 0.84 in NHANES. By risk score, 72% of occult-reduced eGFR cases were detected by screening only 22% of participants.
  
  
  CONCLUSIONS
  A risk score using characteristics readily accessible in clinical practice can identify the majority of persons with reduced eGFRcys, which is missed by creatinine.
authors.affiliation: San Francisco Veterans Affairs Medical, San Francisco, Calif., USA.
authors.forename: Carmen A
authors.initials: CA
authors.lastname: Peralta
authors.forename: Paul
authors.initials: P
authors.lastname: Muntner
authors.forename: Rebecca
authors.initials: R
authors.lastname: Scherzer
authors.forename: Suzanne
authors.initials: S
authors.lastname: Judd
authors.forename: Mary
authors.initials: M
authors.lastname: Cushman
authors.forename: Michael G
authors.initials: MG
authors.lastname: Shlipak
mesh_terms: D001741:Black or African American / Q000706:statistics & numerical data; D000368:Aged; D000369:Aged, 80 and over; D001499:Bayes Theorem; D015992:Body Mass Index; D015331:Cohort Studies; D003404:Creatinine / Q000378:metabolism*; D055316:Cystatin C / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000453:epidemiology; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism; D012306:Risk; D012907:Smoking / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data
chemical_list: D055316:Cystatin C; D003404:Creatinine