Is a nitrite positive result with mild leukocyturia (White Blood Cell count 1-3) and a negative leukocyte esterase test indicative of a Urinary Tract Infection (UTI)?

Nitrite Positive with Minimal Leukocyturia and Negative Leukocyte Esterase in UTI Diagnosis

A nitrite positive result with minimal leukocyturia (WBC 1-3) and negative leukocyte esterase is not sufficient to definitively diagnose a UTI, and a urine culture should be obtained to confirm the diagnosis. 1

Interpretation of Urinalysis Findings

The diagnostic value of individual urinalysis components varies:

• Nitrite test:

  • High specificity (98%) but lower sensitivity (53%) 1
  • Positive result strongly suggests presence of nitrite-producing bacteria
  • False negatives can occur with non-nitrite producing organisms (e.g., Enterococcus) 2

• Leukocyte esterase:

  • Moderate sensitivity (83%) and specificity (78%) 1
  • Negative result in this case reduces likelihood of UTI
  • Important marker of pyuria/inflammation

• WBC count:

  • WBC 1-3 represents minimal leukocyturia
  • True pyuria is typically defined as ≥5-10 WBCs/HPF 1
  • Absence of significant pyuria may indicate asymptomatic bacteriuria rather than true UTI

Clinical Decision Making

According to the American Academy of Pediatrics guidelines, both an abnormal urinalysis result AND a positive urine culture are needed to confirm UTI 3. The combination of leukocyte esterase and nitrite provides the highest diagnostic accuracy (sensitivity 93%, specificity 72%) 1.

In this case:

1. Positive nitrite suggests presence of bacteria
2. Negative leukocyte esterase and minimal WBCs suggest absence of significant inflammation
3. This pattern may represent:
   • Early UTI before inflammatory response develops
   • Asymptomatic bacteriuria (bacteria without true infection)
   • False positive nitrite test

Recommended Approach

1. Obtain a urine culture to confirm or exclude infection 1

   • Culture is essential when urinalysis findings are discordant
   • Positive culture defined as ≥50,000 CFU/mL 3

2. Consider clinical context:

   • Presence of symptoms (dysuria, frequency, urgency)
   • Patient risk factors (pregnancy, immunocompromised status)
   • Recent antibiotic use that might affect urinalysis results

3. Interpret based on patient population:

   • In pregnant women: treat all bacteriuria (even asymptomatic) 1
   • In elderly/catheterized patients: avoid overdiagnosis of UTI based on bacteriuria alone 1
   • In children: culture is particularly important as pyuria may be absent in certain infections 4

Important Caveats

• Poor predictive value: Studies show urinalysis alone has limited sensitivity for detecting UTI 5
• Organism-specific patterns: Some bacteria like Klebsiella and Enterococcus may cause UTI with less pyuria 4
• Processing time matters: Urine specimens should be processed within 1 hour at room temperature or 4 hours if refrigerated to maintain accuracy 1
• Asymptomatic bacteriuria: Presence of bacteria without significant pyuria often represents colonization rather than infection and generally should not be treated except in pregnancy 1

The discordant pattern of positive nitrite with negative leukocyte esterase and minimal WBCs requires culture confirmation before making a definitive diagnosis of UTI.