A new chemical preservative that permits analysis of urine sediment for light microscopic examination 12 h after emission

Introduction: Urine diagnosis by light microscopy is considerably more diff icult when specimens are analyzed after a certain period of time. Objective s: (1) To investigate whether this change effectively exists at a significa nt level of 12 h. (2) To apply measures, once the above has been done, allo wing for the analysis of samples beyond 12 h in similar conditions. Materia ls and Methods: Both freshly produced urine and pathological samples were u sed 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 chemic al 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 s olution of pH 7.35 at 25 degrees C room temperature. Urinalysis was carried out on all samples: glucose (enzymatic method of hexokinase) and total pro tein in liquid (red pyrogallol method). Centrifugation was followed by sedi ment analysis with light microscopy. Statistical analysis was done with the Kolmogorov-Smirnov normality test, Friedman nonparametric test and multipl e comparisons. Results and Conclusion: Urine samples tested 12 h after havi ng 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 an y 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).