title: A new chemical preservative that permits analysis of urine sediment for light microscopic examination 12 h after emission.
abstract: BACKGROUND
  Urine diagnosis by light microscopy is considerably more difficult when specimens are analyzed after a certain period of time.
  
  
  OBJECTIVE
  (1) To investigate whether this change effectively exists at a significant level of 12 h. (2) To apply measures, once the above has been done, allowing for the analysis of samples beyond 12 h in similar conditions.
  
  
  METHODS
  Both freshly produced urine and pathological samples were used under certain experimental conditions: initial, 12 h, 12 h + fridge at 4 degrees C (F), 12 h + chemical preservation (S) and 12 h + SF. The chemical preservative was prepared at a 50/50 ratio with 3% formaldehyde and 2.5% glutaraldehyde by the addition of a buffer of pH 7.2-7.4, resulting in a solution of pH 7.35 at 25 degrees C room temperature. Urinalysis was carried out on all samples: glucose (enzymatic method of hexokinase) and total protein in liquid (red pyrogallol method). Centrifugation was followed by sediment analysis with light microscopy. Statistical analysis was done with the Kolmogorov-Smirnov normality test, Friedman nonparametric test and multiple comparisons.
  
  
  CONCLUSIONS
  Urine samples tested 12 h after having been produced changed significantly (p<0.0001), making it necessary to adopt certain measures to maintain their initial conditions. In our case, after the addition of the chemical preservative, samples did not present any changes (p>0.10) in relation to the initial conditions and were seen to be reliable, therefore indicating the suitability and effectiveness of the analytical conditions (urinalysis in particular, sediment analysis).
authors.affiliation: Service of Clinical Biochemistry, University Hospital of Granada, Spain.
authors.forename: M
authors.initials: M
authors.lastname: del Rosario Rodríguez Moreno
authors.forename: I
authors.initials: I
authors.lastname: Rodríguez Moreno
authors.forename: M T
authors.initials: MT
authors.lastname: León
authors.forename: M
authors.initials: M
authors.lastname: Boy
authors.forename: N
authors.initials: N
authors.lastname: Cowdry Agnieszka
mesh_terms: D004912:Erythrocytes / Q000166:cytology; D005557:Formaldehyde; D006801:Humans; D007962:Leukocytes / Q000166:cytology; D013048:Specimen Handling / Q000379:methods; D013997:Time Factors; D016482:Urinalysis / Q000379:methods*; D014556:Urine / Q000166:cytology* / Q000382:microbiology
chemical_list: D005557:Formaldehyde