Cancer Diagnosis Program | Biorepositories and Biospecimen Research Branch

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Comparison of urine contamination rates using three different methods of collection: clean-catch, cotton wool pad and urine bag.

Author(s): Alam MT, Coulter JB, Pacheco J, Correia JB, Ribeiro MG, Coelho MF, Bunn JE

Publication: Ann Trop Paediatr, 2005, Vol. 25, Page 29-34

PubMed ID: 15814046 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study compared contamination rates of clean-catch urine with urine collected in pads (wool or sanitary) or bags from hospitalized children less than three years old without UTI. When possible, urine specimens were collected by each of the three methods from the 191 patients on the same day but if necessary, collection was continued the next day.  Collection in wool pads involved placing Newcastle pads (first 110 patients) or cotton sanitary pads (59 patients) inside the diaper and checking every 10 minutes to determine when wet. When the pad was wet, urine was aspirated into a syringe. To collect clean-catch urine specimens, the child sat on the parent’s lap not wearing a diaper until the specimen was collected. Urine was refrigerated until analyzed by contrast phase microscopy within 1 h and culture, which occurred within 2 h. The patient was considered to have a urinary tract infection when more than 105 cfu/ml bacteria were found by all three methods and the specimens were excluded. Similarly, specimens were excluded if the patient was considered indeterminate (at least one specimen considered positive for UTI). Any growth on culture was considered positive for contaminants.

   Summary of Findings:

   Twelve of the 191 patients (6.3%) were found to have UTI and three patients were indeterminate for UTI, thus urine from 15 patients was excluded from further analysis.  At least one contaminated specimen was collected from 76 of the 160 included patients who provided urine by all three methods (47.5%).

   Collection by the clean-catch method resulted in significantly less contamination than collection on pads (14.7% versus 29%, P<0.01) or bags (14.7% versus 26.6%, P<0.01). Collection on sanitary pads rather than the Newcastle pads resulted in non-significant increases in contamination rates (36% versus 26%). Only slight agreement was observed between clean-catch and bag (22%) or pad specimens (20%), but there was moderate agreement between bag and pads (40%). Contamination by the clean-catch method was non-significantly lower in boys than girls (12% versus 19%) and the authors report comparable contamination in specimens from boys and girls when collected in bags or pads. The number of specimens that were culture positive increased with an increase in bacteria observed by microscopy.  Using a cut-off or ≤10 bacteria/five small squares; microscopy properly classified 76.3% of negative specimens and 48.4% of contaminated specimens.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • Other Preservative

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Cell count/volume	Microbiological assay
   Cell count/volume	Light microscopy

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Preaquisition	Patient gender	Female Male
   Biospecimen Acquisition	Method of fluid acquisition	Different urine collection procedures compared Voided urine (spot collection)
   Microbiological assay Specific	Technology platform	Phase-contrast microscopy

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