Importance of pre-analytical for urinalysis with urinary crystals.

Crystalluria is an imbalance between promoters and inhibitors; the first are the engine of the crystals and the second are made of substances. The biological assays make it possible to demonstrate one or more lithogenic factors observed during the lithiasis. The objective of our work was to study the impact of acidification or alkalization of the urine of lithiasic patients during a cristallurie assessment. All urine in the morning must be stored at room temperature and examined within two-three hours following voiding. 80 lithiasic patients (40 for urinary calcium and 40 for urinary uric acid) were selected from the results of cristalluria: more than 20 calcium-dependent crystals or uric acid crystal/mm. For calcium and uric acid, concentration differences, after acidification and alkalization are observed: r=0.43 (p<0.01) and r=0.36 (p<0.01) respectively. In conclusion, in this lithiasic population with the presence of cystals, this pre-analytical stage is essential for urinary calcium and uric acid, making it possible to establish a diagnosis of certainly for the patient.