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September 1995

Explanation for False-positive Urine Cultures Obtained by Bag Technique

Author Affiliations

Department of Pediatric Nephrology The Children's Hospital 890 W Faris Rd Suite 250, Box 1 Greenville, SC 29605-4253
Calgary, Alberta

Arch Pediatr Adolesc Med. 1995;149(9):1042. doi:10.1001/archpedi.1995.02170220107023

The well-designed study by Schlager et al1 in the February issue of the Archives demonstrated that the periurethral area was colonized with a potential urinary pathogen in 20 (20%) of 98 newborns. The periurethral area was colonized only in female and uncircumcised male newborns; none of the circumcised male newborns had positive periurethral swab cultures. Whenever the periurethral area was colonized, a urine specimen obtained by bag technique grew the same bacteria.1

Some readers might infer from this study that a bag urine specimen is unreliable for the diagnosis of urinary tract infection (UTI). What Schlager et al2 have shown is that when the clinical suspicion of UTI is low—such as in the newborn period, when the symptoms of UTI are often nonspecific—a bag specimen has a high rate of false-positive results. When the clinical suspicion of UTI is low, a suprapubic aspiration or in-and-out catheter might

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