What is the diagnostic and treatment approach for a patient presenting with symptoms suggestive of a urinary tract infection (UTI)?

Urinalysis in Suspected Urinary Tract Infection

Urinalysis should be performed in all patients with symptoms suggestive of UTI, using dipstick or microscopic examination to detect pyuria (≥10 WBCs/high-power field) and/or bacteriuria, with urine culture reserved for specific clinical scenarios rather than routine use in uncomplicated cases. 1, 2

When to Perform Urinalysis

Routine Urinalysis is Indicated For:

• All patients presenting with acute UTI symptoms (dysuria, frequency, urgency, hematuria, suprapubic pain) 1, 2
• Febrile infants and children 2-24 months with suspected infection 1
• Patients with overactive bladder symptoms to exclude infection and hematuria 1
• Older adults in long-term care facilities with acute onset of UTI-associated symptoms (fever, dysuria, gross hematuria, new/worsening incontinence) 1

When Urinalysis Should NOT Be Performed:

• Asymptomatic patients - do not screen for asymptomatic bacteriuria except in pregnancy or before urological procedures breaching mucosa 1, 2
• Long-term care residents without acute symptoms - routine screening is not recommended 1
• Spinal cord injury patients without symptoms - routine dipstick testing should not be used 1

Diagnostic Approach

For Uncomplicated UTI in Women:

Women with classic symptoms (dysuria, frequency, urgency) may be treated empirically without urinalysis, as dysuria alone has high diagnostic accuracy 2. However, urinalysis adds value when:

• Diagnostic uncertainty exists
• Symptoms are atypical
• Patient has recurrent UTIs requiring documentation 2, 3

Urinalysis Components and Interpretation:

Dipstick Testing 1, 3:

• Leukocyte esterase: 83% sensitivity, 78% specificity
• Nitrite: 53% sensitivity, 98% specificity (requires 4 hours in bladder)
• Combined leukocyte esterase OR nitrite: 93% sensitivity, 72% specificity

Microscopic Examination 1:

• Pyuria (≥10 WBCs/HPF): 73% sensitivity, 81% specificity
• Bacteriuria: 81% sensitivity, 83% specificity - more specific than pyuria 3

Critical caveat: In patients with high pretest probability based on symptoms, negative dipstick does not rule out UTI 3. Conversely, pyuria without symptoms (especially in elderly or catheterized patients) does not indicate infection requiring treatment 1.

When to Add Urine Culture

Mandatory Culture Situations 2:

• Suspected pyelonephritis or urosepsis (obtain before antibiotics)
• Pregnant women (culture is gold standard despite positive dipstick)
• Symptoms not resolving or recurring within 4 weeks after treatment
• Recurrent UTIs requiring documentation
• Patients with complicating factors (immunosuppression, structural abnormalities, neurogenic bladder)

Culture Threshold:

• ≥50,000 CFU/mL from catheterized specimen establishes UTI diagnosis 1
• Even 10² CFU/mL may reflect infection in symptomatic women 3
• Culture results should guide antibiotic adjustment from empiric therapy 1, 2

Special Population Considerations

Long-Term Care Residents 1:

• Perform CBC with differential (including manual differential for bands) within 12-24 hours of symptom onset
• Urinalysis only for residents with acute onset of fever, dysuria, gross hematuria, or new incontinence
• If pyuria present on dipstick, then order culture
• For suspected urosepsis: obtain urine culture, blood culture, and Gram stain of uncentrifuged urine

Catheterized Patients 1:

• Change catheter before specimen collection if long-term catheter present
• Pyuria is universal and has no predictive value
• Only test when systemic symptoms present (fever, hypotension, altered mental status)

Pediatric Patients (2-24 months) 1:

• Obtain specimen via catheterization or suprapubic aspiration (not bag collection for culture)
• Bag specimens with positive results require confirmation via catheterization
• Fresh specimen required (≤1 hour at room temperature or ≤4 hours refrigerated)

Treatment Implications

First-line empiric therapy while awaiting culture (if obtained) 2, 4:

• Nitrofurantoin
• Trimethoprim-sulfamethoxazole (if local resistance <20%)
• Fosfomycin

Duration: 3-7 days for uncomplicated UTI 2, 5

Adjust therapy based on culture results and local resistance patterns 1, 2

Common Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria - even with positive urinalysis, treatment increases resistance without benefit (except pregnancy/pre-procedure) 1, 2
• Do not rely solely on pyuria in elderly or catheterized patients - it lacks specificity in these populations 1, 3
• Do not delay empiric treatment waiting for culture in symptomatic patients with high pretest probability 2
• Do not order routine cultures for uncomplicated UTI in otherwise healthy women - adds cost without changing management 5, 2
• Avoid treating non-specific symptoms (confusion, functional decline) as UTI in elderly without localizing urinary symptoms 1