Appraisal of the stability of leukocytes in refrigerated urine

There is limited evidence that urinary leukocytes are rapidly destroyed in alkaline hypotonic urine. We assessed the stability of leukocytes in urine specimens provided by 90 children with neurogenic bladder who attended a meningomyelocele clinic. No significant correlation was found between urine specific gravity and leukocyte survival after an interval of 4 h in a sample of 30 specimens from these patients. The survival of leukocytes was determined at 2 h and at 4 h in aliquots of these 30 specimens directly, and after adjustment to pH values of 5.0, 7.0, 8.0, 8.5, and 9.0. Statistically significant leukocyte destruction only occurred at pH 9.0 at 2 h (16%), at pH 8.5 at 4 h (19%), and at pH 9.0 at 4 h (57%). Only one of a further sample of 180 routine specimens had both a pH of > or = 8.5 and an interval to laboratory examination of > 2 h. No specimen had a specific gravity of < 1.002, and 93.9% had values of > or = 1.005. Urine pH and tonicity were not therefore important determinants of leukocyte stability in refrigerated samples examined within 4 h from this clinic population.