What is the appropriate management for infants and children over 3 months old with suspected Urinary Tract Infections (UTIs) based on urine dipstick testing results?

Urine Dipstick Testing for Suspected UTI in Infants and Children >3 Months Old

For infants and children >3 months old with suspected UTI, urine dipstick testing should be used as the initial screening tool, with negative leukocyte esterase AND negative nitrite results ruling out UTI without the need for microscopy or culture, while positive results for either parameter should prompt antibiotic treatment and urine culture. 1

Interpreting Urine Dipstick Results

Negative Dipstick Results

• When both leukocyte esterase AND nitrite are negative, the probability of UTI is very low (<0.3%), making it appropriate to withhold antibiotic treatment and avoid sending urine for microscopy and culture 1, 2
• The combination of negative leukocyte esterase and negative nitrite has excellent negative predictive value, effectively ruling out UTI in most cases 3, 4

Positive Dipstick Results

• If either leukocyte esterase OR nitrite (or both) are positive, start antibiotic treatment and send a urine sample for culture 1
• The combination of leukocyte esterase OR nitrite positive increases sensitivity to 93%, making it an effective screening approach 2, 5
• Positive nitrite has excellent specificity (98%) but limited sensitivity (53%), meaning a positive result strongly suggests UTI 1
• Leukocyte esterase has better sensitivity (83%) but lower specificity (78%) compared to nitrites 1

Urine Collection Methods

For Toilet-Trained Children

• Clean catch/midstream urine sample is the recommended collection method 1
• This method minimizes contamination while avoiding invasive procedures 1

For Non-Toilet-Trained Children

• Catheterization or suprapubic aspiration (SPA) is recommended for definitive diagnosis 1
• Bag urine specimens are not suitable for culture due to high contamination rates 1
• A "positive" culture result from a specimen collected in a bag cannot be used to document a UTI; confirmation requires culture of a specimen collected through catheterization or SPA 1

Diagnostic Criteria for UTI

• The diagnosis of UTI requires both:
  1. Urinalysis results suggesting infection (pyuria and/or bacteriuria)
  2. Positive urine culture with ≥50,000 CFU/mL of a uropathogen 1
• Urine specimens must be fresh (processed within 1 hour at room temperature or 4 hours if refrigerated) to ensure accurate results 1, 2

Antibiotic Treatment Considerations

• Start empiric antibiotics when leukocyte esterase or nitrite is positive while awaiting culture results 1
• Choose antibiotics effective against common uropathogens according to local sensitivity patterns 1
• Common options include:
  • Trimethoprim/sulfamethoxazole for children >2 months of age 6
  • Cefixime for children ≥6 months of age 7
• Adjust antimicrobial therapy according to culture sensitivities once available 1

Common Pitfalls to Avoid

• Do not rule out UTI based solely on negative nitrite results, as this would miss many true infections due to the test's limited sensitivity 2, 5
• Do not diagnose UTI based on positive culture alone without evidence of pyuria, as this may represent asymptomatic bacteriuria rather than true infection 2, 3
• Avoid collecting specimens in urine bags for definitive diagnosis; while negative results may be useful, positive results require confirmation with catheterization or SPA 1
• Remember that frequent voiding in infants may lead to false-negative nitrite results due to insufficient bladder dwell time 3, 8