title: Using 24-hour urinalysis to predict stone type.
abstract: OBJECTIVE
  We determined the accuracy of 24-hour urinalysis in predicting stone type and identify the associations between 24-hour urine elements with stone type.
  
  
  METHODS
  We performed a retrospective review of 503 stone formers with stone composition analysis and 24-hour urinalysis available. Analysis of 24-hour urine elements across stone types was performed using Fisher's exact test and ANOVA. Multinomial logistic regression was used to predict stone type based on 24-hour urinalysis.
  
  
  RESULTS
  A total of 280 (56%) patients had predominantly calcium oxalate, 103 (20%) had uric acid, 93 (19%) had calcium phosphate, 16 (3%) had mixed and 11 (2%) had other stone types. There were several significant patient characteristics and 24-hour urinalysis differences across stone type groups. The statistical model predicted 371 (74%) calcium oxalate, 78 (16%) uric acid, 52 (10%) calcium phosphate, zero mixed and 2 (less than 1%) other stone types. The model correctly predicted calcium oxalate stones in 85%, uric acid in 51%, calcium phosphate in 31%, mixed in 0% and other stone types in 18% of the cases. Of the predicted stone types, correct predictions were 61%, 69%, 56% and 71% for calcium oxalate, uric acid, calcium phosphate and other stones types, respectively. The overall accuracy was 64%. Plots were used to explore the associations between each 24-hour urine element with each predicted stone type adjusted for all the others urinary elements.
  
  
  CONCLUSIONS
  A 24-hour urinalysis alone does not accurately predict stone type. However, it may be used in conjunction with other variables to predict stone composition.
authors.affiliation: Arthur Smith Institute for Urology, Hosftra North Shore-LIJ School of Medicine, New Hyde Park, New York. Electronic address: dmoreira@nshs.edu.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Moreira
authors.forename: Justin I
authors.initials: JI
authors.lastname: Friedlander
authors.forename: Christopher
authors.initials: C
authors.lastname: Hartman
authors.forename: Sammy E
authors.initials: SE
authors.lastname: Elsamra
authors.forename: Arthur D
authors.initials: AD
authors.lastname: Smith
authors.forename: Zeph
authors.initials: Z
authors.lastname: Okeke
mesh_terms: D002129:Calcium Oxalate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013997:Time Factors; D014527:Uric Acid / Q000032:analysis; D016482:Urinalysis / Q000379:methods*; D014545:Urinary Calculi / Q000145:classification / Q000652:urine*
chemical_list: D002130:Calcium Phosphates; D002129:Calcium Oxalate; D014527:Uric Acid; C020243:calcium phosphate
keywords: BMI; DM; HTN; SS; body mass index; calcium oxalate; calcium phosphate; diabetes mellitus; hypertension; kidney calculi; supersaturation; uric acid; urinalysis