Pyuria and Urine Concentration for Identifying Urinary Tract Infection in Young Children

Abstract

OBJECTIVES: Accuracy of pyuria for urinary tract infection (UTI) varies with urine concentration. Our objective of this study was to determine the optimal white blood cell (WBC) cutoff for UTI in young children at different urine concentrations as measured by urine specific gravity. METHODS:Retrospective cross-sectional study of children ,24 months of age evaluated in the emergency department for suspected UTI with paired urinalysis and urine culture during a 6year period. The primary outcome was positive urine culture result as described in the American Academy of Pediatrics clinical practice guideline culture thresholds. Test characteristics for microscopic pyuria cut points and positive leukocyte esterase (LE) were calculated across 3 urine specific gravity groups: low ,1.011, moderate 1.011 to 1.020, and high .1.020.RESULTS: Of the total 24 171 patients analyzed, urine culture result was positive in 2003 (8.3%). Urine was obtained by transurethral in-and-out catheterization in 97.9%. Optimal WBC cutoffs per high-power field (HPF) were 3 (positive likelihood ratio [LR1] 10.5; negative likelihood ratio [LR2] 0.12) at low, 6 (LR1 12; LR2 0.14) at moderate, and 8 (LR1 11.1; LR2 0.35) at high urine concentrations. Likelihood ratios for small positive LE from low to high urine concentrations (LR1 25.2, LR2 0.12; LR1 33.1, LR2 0.15; LR1 37.6, LR2 0.41) remained excellent.CONCLUSIONS: Optimal pyuria cut point in predicting positive urine culture results changes with urine concentration in young children. Pyuria thresholds of 3 WBCs per HPF at low urine concentrations whereas 8 WBCs per HPF at high urine concentrations have optimal predictive value for UTI. Positive LE is a strong predictor of UTI regardless of urine concentration.WHAT'S KNOWN ON THIS SUBJECT: The accuracy of pyuria for urinary tract infection varies with urine concentration in children. Previously, optimal diagnostic white blood cells (WBCs) per high-power field (HPF) cutoffs for pyuria have been established at 2 different urine concentrations.WHAT THIS STUDY ADDS: With this study, we identify optimal WBCs per HPF cut points for pyuria at 3 different urine concentrations. WBCs per HPF cutoffs of 3 at low, 6 at medium, and 8 at high urine concentrations should be used to improve pyuria accuracy for urinary tract infection in young children.

Diagnostic value of biomarkers for paediatric urinary tract infections in primary care: systematic review and meta-analysis

“…Bias was present for patient selection, caused by retrospective sampling ( n = 20) [ 16 , 19 , 24 , 34 – 36 , 38 , 43 , 50 , 52 , 53 , 69 , 71 , 74 , 76 , 81 , 82 , 86 , 88 , 90 ], convenience sampling ( n = 8) [ 21 , 37 , 39 , 41 , 46 , 51 , 61 , 65 ], or including a narrow spectrum of patients ( n = 4) [ 72 , 77 , 83 , 90 ]. All retrospective studies were considered at high risk for selection bias, because these studies might overestimate the diagnostic accuracy of the index test [ 26 ].…”

Predicting urine culture results in candidates for lithotripsy

“…[8] Several attempts were made to identify preoperative risk factors of positive urine culture. [9,10] A recent meta-analysis showed that sex, preoperative ureteric stent insertion, and diabetes mellitus were associated with positive urine cultures in patients before URS. [11] In another study, a stone diameter greater than 2 cm was a risk factor in patients undergoing RIRS.…”