Does a white blood cell (WBC) count in urine alone indicate a urinary tract infection (UTI)?

White Blood Cells Alone Do Not Indicate UTI in Urine

White blood cells (WBC) alone in urine are not sufficient to diagnose a urinary tract infection (UTI) and must be accompanied by symptoms and other diagnostic findings. 1, 2

Diagnostic Approach for UTI

Initial Evaluation

• Urinalysis should be performed first as a screening test before proceeding to urine culture for patients with suspected UTI 1
• The minimum laboratory evaluation for suspected UTI should include:
  • Urinalysis for determination of leukocyte esterase and nitrite level by dipstick
  • Microscopic examination for WBCs 3
• Only if pyuria (≥10 WBCs/high-power field) or a positive leukocyte esterase or nitrite test is present on dipstick should a urine culture be ordered 3

Interpreting Urinalysis Results

• Leukocyte esterase has higher sensitivity (83-94%) but lower specificity (78-91%) for detecting UTIs 1
• Nitrite testing has higher specificity (98%) but lower sensitivity (53%) for UTI detection 1
• The absence of pyuria has excellent negative predictive value and can effectively rule out UTI 1, 2
• WBC in urine without symptoms is insufficient for UTI diagnosis as asymptomatic bacteriuria is common (15-50% in non-catheterized long-term care facility residents) 3

Clinical Decision Making

When to Suspect UTI

• Diagnostic evaluation should be reserved for patients with acute onset of UTI-associated symptoms 3:
  • Fever
  • Dysuria
  • Gross hematuria
  • New or worsening urinary incontinence
  • Suspected bacteremia 3
• In residents with long-term indwelling urethral catheters, evaluation is indicated only if there is suspected urosepsis (fever, shaking chills, hypotension, or delirium) 3

Common Pitfalls to Avoid

• Treating asymptomatic bacteriuria leads to unnecessary antibiotic use and resistance 2
• Relying solely on dipstick results without considering clinical symptoms leads to overtreatment 2
• Non-specific symptoms in elderly patients (confusion, anorexia, functional decline) are often not associated with UTIs despite being commonly attributed to them 3

Special Populations

Elderly Patients

• Urinalysis and urine cultures should not be performed for asymptomatic residents 3
• Asymptomatic bacteriuria in LTCF residents without long-term indwelling urinary catheters can persist for 1-2 years without increased morbidity or mortality 3
• Avoid treating based on non-specific symptoms without specific urinary symptoms 2

Pediatric Patients

• For children younger than 2 years with suspected UTI, a urine culture should be obtained in conjunction with urinalysis 1
• In infants aged 2-6 months, urine dipstick (≥1+ leukocyte esterase or positive nitrite) has higher sensitivity (90.2%) and specificity (92.6%) than urine WBC count for diagnosing UTI 4

Specimen Collection

• Appropriately collected urine specimens include a mid-stream or clean-catch specimen from cooperative and functionally capable patients 3, 1
• For women, in-and-out catheterization may be required 3
• For residents with long-term indwelling urethral catheters and suspected urosepsis, catheters should be changed prior to specimen collection and antibiotic therapy 3, 1