Related Experiment Video
Updated: Jul 20, 2026

Cell-Free DNA Integrity Analysis in Urine Samples
Published on: January 5, 2017
[Is the technique used to collect urine important in avoiding contamination of samples?]
V R Cabedo García1, C Novoa Gómez, M D Tirado Balaguer
1Médico de Familia, Centro de Salud El Barranquet, Larga 70, 12005 Castellón, Spain. vcabedog@meditex.es
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.
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