Urine dipstick low sensitivity for UTI diagnosis in febrile infants^**

Background: Urine cultures are usually obtained from 0- to 2-month-old febrile infants, while in older children they are obtained more selectively. In 3- to 23-month-old children, urinary tract infection (UTI) diagnosis requires both positive culture and dipstick, but data are scarce regarding 0- to 2-month-old infants. We assessed dipstick performance for UTI diagnosis in 0–2 vs. 3- to 23-month-old children.

Methods: A case–control study, conducted between 2015 and 2016, in southern Israel. Sensitivity and specificity of urine dipstick for diagnosing UTI were assessed. We compared dipstick false-negative (FN) and true-positive (TP) groups; high FN rate indicates low sensitivity.

Results: Overall, 434 positive and 571 sterile urine culture episodes were included. Dipstick sensitivity was 63% in 0-2 month old children; 93% for supra-pubic aspiration (SPA), and ∼50% for non-SPA sampling method. However, sensitivity was >90% for 3–5 and 6- to 23-month-old children. In univariate analysis, younger age, hospitalization, lower temperature, short fever duration, lower leukocyte blood levels, neutrophils, stabs and C-reactive protein, and absent future UTI within <1 year were associated with FN compared with TP. In multivariate analysis, among positive culture episodes, age 0–2 months (odds ratio, OR = 6.60) and non-SPA sampling method (OR = 8.39) were associated with FN episodes.

Conclusions: Dipstick lower sensitivity for diagnosing UTI in febrile infants 0–2 months old vs. their older counterparts, was associated with non-SPA sampling method, lower inflammatory markers, lower temperature and low risk for future UTI. This suggests that positive culture in negative dipstick episodes may not reflect a true UTI.