[Systematic review of the validity of urine cultures collected by sterile perineal bags]

Abstract

Introduction: The perineal adhesive bag is the most used method in our country for urine culture collection in infants, despite having a high risk of contamination and false-positive results. We aim to quantify both types of risks through a systematic review.

Methods: Search updated in May 2014 in PUBMED, SCOPUS (includes EMBASE), IBECS; CINAHL, LILACS AND CUIDEN, without language or time limits. Percentages of contaminated urines, false positives, sensitivity and specificity (with respect to catheterization or bladder puncture) were recorded.

Results: A total of 21 studies of medium quality (7,659 samples) were selected. The pooled percentage of contaminated urines was 46.6% (15 studies; 6856 samples; 95% confidence interval [95% CI]: 35.6 to 57.8%; I(2): 97.3%). The pooled percentage of false positives was 61.1% (12 studies; 575 samples; 95% CI: 37.9 to 82.2%; I(2): 96.2%). Sensitivity (88%; 95% CI: 81-93%; I(2): 55.2%), and specificity (82%; 95% CI: 75-89%; I(2): 41.3%) were estimated in five studies, but without including contaminated urines.

Conclusion: The perineal adhesive bag is not a valid enough method for urine culture collection, because almost half are contaminated and, if they are positive, two out of three are false. Although these estimates are imprecise, because of their great heterogeneity, they should be considered when choosing the method of urine collection. The estimates of sensitivity and specificity are not applicable because they do not take into account the risk of contamination.

Keywords: Infección urinaria; Meta-analysis; Metaanálisis; Orina/microbiología; Recogida de muestra de orina; Sensibilidad y especificidad; Sensitivity and specificity; Urinary tract infections; Urine specimen collection; Urine/microbiology.