URINE CULTURE CONTAMINATION - A COLLEGE-OF-AMERICAN-PATHOLOGISTS Q-PROBES STUDY OF CONTAMINATED URINE CULTURES IN 906 INSTITUTIONS

Objective.-To examine the frequency and causes of urine culture contam ination in outpatients. Methods.-Nine hundred six institutions, rangin g in size from less than 50 to more than 600 beds, each examined 250 c onsecutively ordered urine cultures from outpatients and identified sp ecimens that met the study definition of contamination. Participants a lso answered questions about the practices used to collect, transport, and process urine specimens. In all, data relating to more than 200 0 00 urine cultures were analyzed. Results.-The median institution repor ted that 18.1% of urine cultures specimens; collected from outpatients were contaminated. The top 10% of institutions (90th percentile) repo rted that 5.6% or fewer of their cultures were contaminated. In contra st, the bottom 10% of institutions (10th percentile) reported that 36. 8% or more of their urine specimens were contaminated. Institutions wi th lower contamination rates tended to process a lower proportion of s pecimens from female patients. Pediatric hospitals also reported lower contamination rates in specimens from children than general hospitals . Other factors, including the use of central processing areas, refrig eration, urine screening systems, specimen preservatives, provision of written collection instructions or special collection kits, and therm ally insulated specimen transport containers, were not found to be ass ociated with low specimen contamination rates in a multivariate analys is. Conclusion.-Contamination of outpatient urine cultures is a common occurrence, and facilities differ significantly in their overall freq uency of urine culture contamination. Many interventions commonly assu med to reduce contamination were not demonstrably effective in this st udy.