title: Evaluation of the appropriate time period between sampling and analyzing for automated urinalysis.
abstract: BACKGROUND
  Preanalytical specifications for urinalysis must be strictly adhered to avoid false interpretations. Aim of the present study is to examine whether the preanalytical factor 'time point of analysis' significantly influences stability of urine samples for urine particle and dipstick analysis.
  
  
  METHODS
  In 321 pathological spontaneous urine samples, urine dipstick (Urisys™2400, Combur-10-Test™strips, Roche Diagnostics, Mannheim, Germany) and particle analysis (UF-1000 i™, Sysmex, Norderstedt, Germany) were performed within 90 min, 120 min and 240 min after urine collection.
  
  
  RESULTS
  For urine particle analysis, a significant increase in conductivity (120 vs. 90 min: P < 0.001, 240 vs. 90 min: P < 0.001) and a significant decrease in WBC (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001), RBC (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001), casts (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001) and epithelial cells (120 vs. 90 min P = 0.610, 240 vs. 90 min P = 0.041) were found. There were no significant changes for bacteria. Regarding urine dipstick analysis, misclassification rates between measurements were significant for pH (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001), leukocytes (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001), nitrite (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001), protein (120 vs. 90 min P < 0.001, 240 vs. 90 min P<0.001), ketone (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001), blood (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001), specific gravity (120 vs. 90 min P < 0.001, 240 vs. 90 min P < 0.001) and urobilinogen (120 vs. 90 min, P = 0.031). Misclassification rates were not significant for glucose and bilirubin.
  
  
  CONCLUSIONS
  Most parameters critically depend on the time window between sampling and analysis. Our study stresses the importance of adherence to early time points in urinalysis (within 90 min).
authors.affiliation: Department of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Bonn, Germany.
authors.forename: Ramona C
authors.initials: RC
authors.lastname: Dolscheid-Pommerich
authors.affiliation: Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany; Institute of Medical Biometry, Informatics and Epidemiology (IMBIE), University Hospital Bonn, Bonn, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Klarmann-Schulz
authors.affiliation: Department of Psychosomatic Medicine and Psychotherapy, University Hospital Bonn, Bonn, Germany.
authors.forename: Rupert
authors.initials: R
authors.lastname: Conrad
authors.affiliation: Department of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Bonn, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Stoffel-Wagner
authors.affiliation: Department of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Bonn, Germany.
authors.forename: Berndt
authors.initials: B
authors.lastname: Zur
mesh_terms: D002452:Cell Count; D004847:Epithelial Cells / Q000166:cytology; D004906:Erythrocyte Count; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007958:Leukocyte Count; D011934:Reagent Strips; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000295:instrumentation / Q000379:methods*; D013997:Time Factors; D016482:Urinalysis / Q000295:instrumentation / Q000379:methods*; D014556:Urine / Q000737:chemistry* / Q000166:cytology; D059349:Urine Specimen Collection / Q000295:instrumentation / Q000379:methods*
chemical_list: D011934:Reagent Strips
keywords: analytical sample preparation methods; automation; flow cytometry; specimen handling; urinalysis