title: Can urine dipstick predict an elevated serum creatinine?
abstract: OBJECTIVE
  Chart review studies have suggested that point-of-care urine dipstick testing may accurately predict an elevation in serum creatinine (Cr). We aimed to prospectively evaluate the test characteristics of proteinuria/hematuria in predicting elevated serum Cr.
  
  
  METHODS
  A prospective, observational study was conducted between March 2007 and June 2008 at 2 affiliated, urban hospitals with an annual emergency department census of 150,000. Patients undergoing laboratory urinalysis, point-of-care urine dipstick, and a serum chemistry panel were enrolled. Trained research assistants collected data on consecutive patients 18 hours per day using preformatted data forms and entry into an anonymized Access (Microsoft, Seattle, Wash) database. Demographic baseline variables including age, sex, chief complaint, vital signs, and source of sample (catheter vs "clean catch") were also collected. An elevated Cr level was defined as greater than 1.3 based on the laboratory reference range. Standard statistical methods were used to calculate diagnostic test operating characteristics of proteinuria or hematuria as a predictor of elevated serum Cr.
  
  
  RESULTS
  Five thousand four hundred sixteen subjects were enrolled with 28.3% male and a mean age of 50.2 years. Elevated serum Cr greater than 1.3 mg/dL was found in 13.9% (755/5416) of subjects. The sensitivity of either proteinuria or hematuria for elevated Cr was 82.5% (95% confidence interval [CI], 80%-85%) and specificity was 34.4% (95% CI, 33%-36%). Positive predictive value was 16.9% (95% CI, 16%-18%) and negative predictive value was 92.4% (95% CI, 91-94%). The likelihood ratio for a positive test was 1.3 (95% CI, 1.1-1.5), and the likelihood ratio for a negative test was 0.5 (95% CI, 0.3-0.8).
  
  
  CONCLUSIONS
  Although negative predictive value was high, the presence of proteinuria/hematuria was only moderately predictive of elevated serum Cr level.
authors.affiliation: St Luke's-Roosevelt Hospital Center, Columbia University, New York, NY 10025, USA. kshah@chpnet.org
authors.forename: Kaushal
authors.initials: K
authors.lastname: Shah
authors.forename: Barbara
authors.initials: B
authors.lastname: Kilian
authors.forename: Wei-Jen
authors.initials: WJ
authors.lastname: Hsieh
authors.forename: Emily
authors.initials: E
authors.lastname: Kyrillou
authors.forename: Vishal
authors.initials: V
authors.lastname: Hedge
authors.forename: David H
authors.initials: DH
authors.lastname: Newman
mesh_terms: D000367:Age Factors; D016001:Confidence Intervals; D003404:Creatinine / Q000097:blood* / Q000652:urine; D005260:Female; D006417:Hematuria / Q000097:blood / Q000175:diagnosis / Q000652:urine; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011507:Proteinuria / Q000097:blood / Q000175:diagnosis / Q000652:urine; D011934:Reagent Strips; D012680:Sensitivity and Specificity; D012737:Sex Factors
chemical_list: D011934:Reagent Strips; D003404:Creatinine