Effect of urine preservation on urine screening and organism identification

Three urine preservation-transport methods were examined for their effect on rapid urine-screening procedures. Results from fresh urine specimens, screened for bacteriuria by leukocyte esterase, nitrate, Autobac, Bac-T-Screen, Auto Microbic System (AMS), and bioluminescence procedures, were compared with urine-screen results from urine specimens held for 24 hours at room temperature in chemical preservatives. Quantitative discrepancies ranged from 0%, for urine preserved with glycerin-boric acid-sodium formate and tested by AMS or leukocyte esterase, to 21% for urines in the same preservative tested by bioluminescence or nitrate. Up to 62% of the organism identifications made from preserved urine specimens tested by the AMS urine card were in error. These data suggest that it may be inadvisable to use weak organic acid-based urine preservation systems in conjunction with these urine-screen procedures.