title: Interpreting the results of chemical stone analysis in the era of modern stone analysis techniques.
abstract: OBJECTIVE
  Stone analysis should be performed in all first-time stone formers. The preferred analytical procedures are Fourier-transform infrared spectroscopy (FT-IR) or X-ray diffraction (XRD). However, due to limited resources, chemical analysis (CA) is still in use throughout the world. The aim of the study was to compare FT-IR and CA in well matched stone specimens and characterize the pros and cons of CA.
  
  
  METHODS
  In a prospective bi-center study, urinary stones were retrieved from 60 consecutive endoscopic procedures. In order to assure that identical stone samples were sent for analyses, the samples were analyzed initially by micro-computed tomography to assess uniformity of each specimen before submitted for FTIR and CA.
  
  
  RESULTS
  Overall, the results of CA did not match with the FTIR results in 56 % of the cases. In 16 % of the cases CA missed the major stone component and in 40 % the minor stone component. 37 of the 60 specimens contained CaOx as major component by FTIR, and CA reported major CaOx in 47/60, resulting in high sensitivity, but very poor specificity. CA was relatively accurate for UA and cystine. CA missed struvite and calcium phosphate as a major component in all cases. In mixed stones the sensitivity of CA for the minor component was poor, generally less than 50 %.
  
  
  CONCLUSIONS
  Urinary stone analysis using CA provides only limited data that should be interpreted carefully. Urinary stone analysis using CA is likely to result in clinically significant errors in its assessment of stone composition. Although the monetary costs of CA are relatively modest, this method does not provide the level of analytical specificity required for proper management of patients with metabolic stones.
authors.affiliation: Sackler School of Medicine, Rabin Medical Center, Tel Aviv University and the Institute of Urology, Petach Tikva, Israel. roni789@gmail.com.
authors.forename: Ron
authors.initials: R
authors.lastname: Gilad
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Williams
authors.affiliation: Sackler School of Medicine, Rabin Medical Center, Tel Aviv University and the Institute of Urology, Petach Tikva, Israel.
authors.forename: Kalba D
authors.initials: KD
authors.lastname: Usman
authors.affiliation: Sackler School of Medicine, Rabin Medical Center, Tel Aviv University and the Institute of Urology, Petach Tikva, Israel.
authors.forename: Ronen
authors.initials: R
authors.lastname: Holland
authors.affiliation: Sackler School of Medicine, Rabin Medical Center, Tel Aviv University and the Institute of Urology, Petach Tikva, Israel.
authors.forename: Shay
authors.initials: S
authors.lastname: Golan
authors.affiliation: Chemical Laboratory, Rabin Medical Center, Petach Tikva, Israel.
authors.forename: Ruth
authors.initials: R
authors.lastname: Tor
authors.affiliation: Sackler School of Medicine, Rabin Medical Center, Tel Aviv University and the Institute of Urology, Petach Tikva, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Lifshitz
mesh_terms: D006801:Humans; D011446:Prospective Studies; D017550:Spectroscopy, Fourier Transform Infrared; D014057:Tomography, X-Ray Computed; D014545:Urinary Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging
keywords: Chemical analysis; FT-IR; Nephrolithiasis; Stone composition