Novel test for the urinary neutrophil gelatinase–associated lipocalin (uNGAL) biomarker have good sensitivity and specificity to distinguish whether infants and children younger than 2 years old have a urinary tract infection (UTI), said Tamar R. Lubell, MD, and her associates at Columbia University, New York.
“NGAL is a protein expressed in neutrophils and several other human tissues, including alpha-intercalated cells in the collecting duct of the kidney,” the researchers explained. “The urine and serum contain very low levels of NGAL protein at steady state, with expression of NGAL rising rapidly in response to cell damage caused by ischemia-reperfusion injury, presence of cytotoxins, and sepsis.”
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Of the 260 children whose catheterized urine was analyzed, 14% had UTIs. The median uNGAL concentration was 215.1 ng/mL in the UTI group, compared with 4.4 ng/mL in the culture-negative group. Urinalysis and Gram stain also were performed.
“uNGAL had higher sensitivity than [urinalysis], with similar specificity,” the investigators said. “Gram stain had a somewhat lower sensitivity than uNGAL, but with high specificity.”
The researchers identified a cutoff point for uNGAL levels to be 39.1 ng/mL. A previous case-control study of 108 infants with UTI had a cutoff for uNGAL levels of 38 ng/mL, with sensitivity of 93% and specificity of 95%. Most urine samples in that study were obtained by clean catch rather than by catheterization, as in the current study.
“Further studies will need to both confirm our findings and determine the benefit and cost effectiveness of uNGAL testing, compared with [urinalysis],” Dr. Lubell and her associates said.
Read more in Pediatrics (2017 Nov 16. doi: 10.1542/peds.2017-1090).