What is the appropriate treatment for a patient with an elevated leukocyte esterase on a urine test indicating a possible urinary tract infection?

Management of Elevated Leukocyte Esterase on Urine Test

A positive leukocyte esterase test on urinalysis should prompt urine culture collection before initiating antimicrobial therapy in patients with symptoms suggestive of urinary tract infection (UTI). 1, 2

Diagnostic Significance

• Leukocyte esterase indicates the presence of white blood cells (pyuria) in urine, which suggests inflammation in the urinary tract 1
• Leukocyte esterase has moderate sensitivity (83%, range 67-94%) but limited specificity (78%, range 64-92%) for detecting UTIs 1
• When combined with nitrite testing, diagnostic accuracy improves significantly with combined sensitivity of 93% and specificity of 96% 1
• The absence of pyuria (negative leukocyte esterase and no microscopic WBCs) has excellent negative predictive value for ruling out UTI 1

Diagnostic Algorithm

1. Determine if symptoms consistent with UTI are present:

   • Dysuria, frequency, urgency, fever, gross hematuria 1
   • In children: fever, irritability, poor feeding 3
   • In older adults: new/worsening urinary incontinence (nonspecific symptoms like confusion alone are insufficient) 1

2. Confirm presence of pyuria:

   • Consider adding nitrite testing (combined testing increases sensitivity to 93%) 1
   • Microscopic examination for WBCs is recommended when leukocyte esterase is positive 1
   • For urine WBC/hpf as a diagnostic test for UTI: LR=19 for WBC count >20/hpf, LR=18.2 for 11-20 WBCs/hpf 3

3. Obtain urine culture before starting antibiotics:

   • Level C recommendation: Physicians should obtain a urine culture when starting antibiotics for the preliminary diagnosis of UTI 3
   • The specimen collection method matters - catheterization is more reliable than bag specimens in children 3

Treatment Recommendations

• For uncomplicated UTI in adults:

  • Trimethoprim/sulfamethoxazole: 4 teaspoonfuls (20 mL) every 12 hours for 10-14 days 4
  • Alternative options include fluoroquinolones or nitrofurantoin based on local resistance patterns 2

• For children with UTI:

  • Trimethoprim/sulfamethoxazole: 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days 4
  • For infants 2 months to 2 years: cephalosporins may be preferred due to increasing resistance to other agents 3, 5

• For patients with impaired renal function:

  • Adjust dosing based on creatinine clearance 4
  • For CrCl 15-30 mL/min: Use half the usual regimen 4
  • For CrCl below 15 mL/min: Use not recommended 4

Special Considerations

• In asymptomatic individuals:

  • Urinalysis and urine cultures should not be performed routinely 1
  • Asymptomatic bacteriuria with pyuria is common in older adults (prevalence 15-50% in non-catheterized long-term care facility residents) 1

• In febrile infants and young children:

  • Level B recommendation: Physicians can use a positive test result for leukocyte esterase to make a preliminary diagnosis of UTI 3
  • In febrile infants with a negative dipstick urinalysis in whom UTI is still suspected, obtain a urine culture 3

• In catheterized patients:

  • Change long-term catheters before collecting specimens, as bacteriuria and pyuria are nearly universal in chronic catheterization 2

Common Pitfalls to Avoid

• Do not rely solely on leukocyte esterase for diagnosis - it has moderate sensitivity (83%) but limited specificity (78%) 1, 6
• Avoid treating asymptomatic bacteriuria in most populations, even with positive leukocyte esterase 1
• In older adults, do not treat based on nonspecific symptoms like confusion or functional decline alone without specific urinary symptoms 1
• Be aware that false-positive results can occur with contaminated specimens, certain oxidizing agents, and some medications 1
• False-negative results may occur with high urinary glucose, high specific gravity, or certain antibiotics 1