[Is the technique used to collect urine important in avoiding contamination of samples?].

OBJECTIVE: To appraise the efficacy of hygienic standards in preventing the contamination of urine samples.

DESIGN: Randomised clinical trial. 515 women assigned at random: 279 to the Intervention group and 236 to Control.

SETTING: Population registered with 4 doctors at 2 health centres.

PARTICIPANTS: Women from 15 to 65 who attended the clinic for on-demand care. Criteria for exclusion from the trial were: permanent bladder catheter, anomalies in genito-urinary apparatus, antibiotic treatment in the 7 previous days and inability to understand instructions.

INTERVENTION: Verbal instructions on hygienic standards for collecting the sample and explanatory leaflet, as against the customary guidelines.

MAIN MEASUREMENTS: The main result was the combination of contamination levels and infection. Analysis by intention to treat.

RESULTS: Irregularities in the urine culture in 113 (41%) patients from the Intervention group and in 133 (56%) from the Control group (P<.001), with RRR of 28% (95% CI, 14%-40%) and NNT of 6 (95% CI, 4-14). Taking only serious contamination or urinary infection, we had 14 in the Intervention group and 36 in the Control (P<.0001), with RRR of 67% (95% CI, 41%-82%) and NNT of 10 (95% CI, 6-20).

CONCLUSIONS: Providing an explanatory leaflet and giving verbal instructions on hygienic standards for urine collection reduces contamination of the samples.