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September 1995

Explanation for False-positive Urine Cultures Obtained by Bag Technique-Reply

Author Affiliations

Department of Pediatrics University of Virginia Health Sciences Center Charlottesville, VA 22908
Chapel Hill, NC
Charlottesville, Va

Arch Pediatr Adolesc Med. 1995;149(9):1042-1043. doi:10.1001/archpedi.1995.02170220107024

We would like to thank Drs Robson and Leung for their comments. As they state, our study does not support the use of bag specimens for the diagnosis of UTIs because a bag specimen results in a high false-positive rate. A bag specimen may be useful, however, when the physician would like to examine the urine in a healthy infant and is willing to withhold antibiotics until urine culture results are reported. If the culture is positive for pathogens, it may be a reflection of the periurethral flora, or it may mean that the urinary tract is infected. To differentiate between periurethral colonization of urine and a UTI, an in-and-out catheter or suprapubic aspiration is recommended for specimen collection. Obviously, if antibiotic therapy has already begun, the diagnosis of periurethral colonization of the urine vs UTI will be impossible to differentiate. Urine bag collection is reliable only if