Three Part Question
In a [non toilet-trained child with suspected UTI] is [clean catch or bag specimen of urine] better at [reducing the risk of contamination and therefore providing an accurate diagnosis of UTI]?
An 18 month old child with fever and vomiting is brought to the Emergency department by its parents. There is no clear focus of infection on clinical examination and you suspect the child has a urinary tract infection. You wonder if a bag specimen of urine or clean catch specimen would be more accurate in diagnosing UTI
Using Medline database 1966 to week 3 November 2005 via OVID.
The Cochrane Library 2005, Issue 4.
CinAHL: CINAHL 1982 to December 2005
Medline: [uti.mp OR exp Urinary Tract Infections] AND [specimen.mp OR exp Specimen Handling/ OR urine bag.mp OR clean catch.mp] AND [BestBETS paediatric filter] LIMIT to human and English language
Cochrane: urinary and specimen and catch
CinAHL: [specimen.mp OR exp Specimen Handling/ OR urine bag.mp OR clean catch.mp]
Medline: 337 papers were found of which 2 were relevant. Cochrane: 17 citations. no new papers found. CinAHL: 100 citations. no new papers found
|Author, date and country
||Study type (level of evidence)
|Hardy et al|
|30 unwell children with suspected UTI||Compared clean catch, bag specimen and suprapubic aspiration of urine||Pure growth or contamination||bag specimens 4/30 pure growth 22/30 contaminated. Clean catch specimens 2/30 pure growth 22/30 mixed growth. Suprapubic aspiration 4/30 pure growth, no contaminated specimens||Children were in-patients in paediatric ward having routine screening. No power study and small numbers.
Authors actually found supra-pubic aspiration to be most effective (but not specifically the topic of this BET)|
|Alam et al|
|191 children, (125 were boys) <3years without known UTI. All children had attempts at clean catch, urine bag and cotton wool pad sampling. If all three results were positive it was declared a positive UTI and excluded from the analysis.||Diagnostic study||Bacterial contamination of three methods of urine sampling.||Clean catch 14.7%, urine bag 26.6%, urine pad 29% (significantly higher than for clean catch p<0.01)||More boys than girls
Exclusion of true UTIs may have biased results.|
|Missing samples (i.e. not obtainable by method)||clean catch (12%), bag (4%), pad (4%).|
There is much debate in the literature about the best technique for collecting urine specimens in children, however little evidence comparing the two methods commonly used in Emergency Departments. Alam et al reveals that clean catch is a better method of obtaining a urine specimen than bag urine, however, both techniques are not 100% sterile and free of contamination, and therefore can produce misleading results. Other methods of obtaining a sterile specimen of urine in non-toilet trained children should be researched, such as supra-pubic aspiration or catheterization. One concern may be that the clean catch specimen is seemingly more difficult to collect (an increased miss rate in the Alam study) and this may present problems in the emergency department setting.
Updated comments and new bottom line by second checker on 14/06/05
Clinical Bottom Line
One study has shown that clean catch is a better non-invasive method of obtaining a urine specimen, compared with bag urine, in non-toilet trained children.
- Hardy JD, Furnell PM, Brumfitt W. Comparison of sterile bag, clean catch and suprapubic aspiration in the diagnosis of urinary tract infection in early childhood Br J Urol 1976;48(4):279-83.
- Alam MT. Coulter JB. Pacheco J. Correia JB. Ribeiro MG. Coelho MF. Bunn JE. Comparison of urine contamination rates using three different methods of collection: clean-catch, cotton wool pad and urine bag. Annals of Tropical Paediatrics. 25(1):29-34, 2005 Mar.