Diagnosing urinary tract infections in young children

Abstract

McGillivray et al1McGillivray D. Mok E. Mulrooney E. Kramer M.S. A head-to-head comparison: ‘clean-void’ bag versus catheter urinalysis in the diagnosis of urinary tract infection in young children.J Pediatr. 2005; 147: 451-456Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar compared the validity of the urinalysis on clean voided bag specimens with catheter urine specimens in the diagnosis of a urinary tract infection (UTI) in young children. Because urine collection by suprapubic aspiration or catheter is not always feasible in children presenting in primary care, we welcome the authors’ finding that the bag dipstick was more sensitive than the catheter dipstick. However, a potential source of bias may have been the cause of this surprising result. The decision to catheterize a child was left to the discretion of the treating physician, who was not blinded to the results of the bag urinalysis. This introduces the possibility of a verification bias in children with a negative bag dipstick. Because not all negative results have been verified by a catheter culture, we do not know the real distribution of test results. To give an indication of the possible bias: Assuming that the distribution of true- and false-negative test results was comparable in the not-included children (prevalence of 8% UTIs in children with a negative bag dipstick), a number of 225 not-included children would decrease the sensitivity of the bag-dipstick from 85% to 70%, which is comparable to the sensitivity of the catheter dipstick. The real magnitude of the effect of this source of bias cannot be estimated because we do not know how the characteristics of the finally included children compare with the characteristics of all eligible children, nor do we know the number of not-included, eligible children. It might well be that the authors can provide us with additional data. For practical reasons, the urinalysis by bag is preferred above urinalysis by catheter in non–toilet-trained children presenting in primary care. The data presented do not allow recommendation of this procedure. ReplyThe Journal of PediatricsVol. 149Issue 6PreviewWe would like to thank Berger et al for their interest in our article, in which we reported that the bag dipstick was more sensitive than the catheter dipstick. Urine obtained by using a bag is more likely to contain bacteria or leukocytes present on perineal skin or in the urethra but not necessarily present in the bladder. The longer dwell time of urine obtained by using bag specimens versus catheter specimens might also increase the number of bacteria and white blood cells, which would increase the yield of positive urinalyses. Full-Text PDF