>>> "David B. Toth" <[log in to unmask]> 09/06/00 04:52AM >>>
>What is the current, unemotional wisdom regarding the method of obtaining a
>urine sample in children?
>Specifically, when would "bagging" be OK? Is it EVER OK?
>Do you really have to cath every child you suspect as having a UTI ???
Based on the recent AAP Practice Parameter: "The Diagnosis, Treatment, and Evaluation of the Initial Urinary Tract Infection in Febrile Infants and Young Children" Pediatrics , 103(4):843-852,1999 - yes, there are situations where it is acceptable to obtain a urine specimen for urinalysis (see Recommendation 4) - in a non-toxic appearing child. However, that urine specimen should not be sent for culture. If the UA is suggestive of UTI, then a second urine specimen should be obtained by catheterization (or suprapubic aspiration) because of the high incidence of false-positive cultures with bagged specimens.
I have simply cut and pasted relevant portions of the above article.
If an infant or young child 2 months to 2 years of age with unexplained fever is assessed as being sufficiently ill to warrant immediate antimicrobial therapy, a urine specimen should be obtained by SPA (supra-pubic aspiration) or transurethral bladder catheterization; the diagnosis of UTI cannot be established by a culture of urine collected in a bag (strength of evidence: good).
If an infant or young child 2 months to 2 years of age with unexplained fever is assessed as not being so ill as to require immediate antimicrobial therapy, there are two options (strength of evidence: good).
Option 1 Obtain and culture a urine specimen collected by SPA or transurethral bladder catheterization.
Option 2 Obtain a urine specimen by the most convenient means and perform a urinalysis. If the urinalysis suggests a UTI, obtain and culture a urine specimen collected by SPA or transurethral bladder catheterization; if urinalysis does not suggest a UTI, it is reasonable to follow the clinical course without initiating antimicrobial therapy, recognizing that a negative urinalysis does not rule out a UTI.
The option with the highest sensitivity is to obtain and culture a urine specimen collected by SPA or transurethral bladder catheterization; however, this approach may be resisted by some families and clinicians. In infants and young children assessed as not being so ill as to require immediate antimicrobial therapy, a urinalysis may help distinguish those with higher and lower likelihood of UTI. The urinalysis can be performed on any specimen, including one collected from a bag applied
to the perineum, and has the advantage of convenience. The major disadvantage of collecting a specimen in a bag is that it is unsuitable for quantitative culture. In addition, there may be a delay of 1 hour or longer for the infant or young child to void; then, if the urinalysis suggests UTI, a second specimen is required. The sensitivity of the bag method for detecting UTI is essentially 100%, but the false-positive rate of this method is also high, as demonstrated in several studies. If the prevalence of UTI is 5%, 85% of positive cultures will be false-positive results; if the prevalence of UTI is 2% (febrile boys), the rate of false-positive results is 93%; if the prevalence of UTI is 0.2% (circumcised boys), the rate of false-positive results is 99%. The use of bag-collected urine specimens persists because collection of urine by this method is noninvasive and requires limited personnel time and expertise. Moreover, a negative (sterile) culture of a bag-collected urine specimen effectively eliminates the diagnosis of UTI, provided that the child is not receiving antimicrobials and that the urine is not contaminated with an antibacterial skin cleansing agent. Based on their experience, many clinicians believe that this collection technique has a low contamination rate under the following circumstances: the patient's perineum is properly
cleansed and rinsed before application of the collection bag; the urine bag is removed promptly after urine is voided into the bag; and the specimen is refrigerated or processed immediately. Nevertheless, even if contamination from the perineal skin is minimized, there may be significant contamination from the vagina in girls or the prepuce in uncircumcised boys.
Published results demonstrate that although a negative culture of a bag-collected specimen effectively rules out UTI, a positive culture does not document UTI. Confirmation requires culture of a specimen collected by transurethral bladder catheterization or SPA. Transurethral catheterization does not eliminate completely the possibility of contamination in girls and uncircumcised boys.
Gershon Segal, MD
Division of Pediatric Emergency Medicine
Johns Hopkins University School of Medicine
600 N. Wolfe St. / CMSC 144
Baltimore, MD 21287-3144
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