Does refrigeration of urine alter culture results in hospitalized patients with neurogenic bladders?

A prospective, blinded study of 40 hospitalized spinal cord injured (SCI) patients was conducted to evaluate the effects of refrigeration on urinalysis and culture results. Urine samples were divided, with one aliquot examined within 4 hours and the other after 24 hours of refrigeration. Comparisons using Wilcoxon Signed Rank analysis showed no significant difference between fresh and refrigerated samples in white blood cell (WBC) count (z = -0.353, p = 0.724), number of bacteria (z = -0.772, p = 0.440), leukocytes (z = -0.277, p = 0.782), or colony counts of E. fecalis, E. coli, Citrobacter, Pseudomonas, Streptococcus, Yeast, or Acinetobacter (z = -1.00, p = 0.317; z = 0.00, p = 1.0; z = 0.00, p = 1.0; z = 0.00, p = 1.0; z = -1.00, p = 0.317; z = 0.00, p = 1.0; z = 0.00, p = 1.0, respectively). A statistically significant difference between fresh and refrigerated samples was found with "mixed" organisms (z = -2.565, p = 0.010) and a difference approaching significance was found with Staph aureus (z = -1.841, p = 0.066), both with colony counts of less than 50 k. No changes in cultures or colony counts occurred following refrigeration that would have resulted in altered treatment regimens. This study indicates that refrigeration of urine samples for up to 24 hours in the hospital setting rarely causes changes in identified organism type and causes no clinically significant changes in urinalysis or urine culture results in SCI patients.