What urine investigations are recommended for a patient with persistent fevers and hospital-acquired pneumonia to rule out a urinary tract infection (UTI)?

Urine Investigations for Persistent Fevers in Hospital-Acquired Pneumonia

For patients with persistent fevers and hospital-acquired pneumonia, urinalysis should be performed only when UTI is suspected based on urinary symptoms or pyuria, and if positive, urine culture should be obtained from a newly replaced catheter.

Initial Assessment for Suspected UTI

• Urinalysis and urine cultures should not be performed routinely in patients with hospital-acquired pneumonia and persistent fevers unless there are specific signs or symptoms suggesting a urinary source 1, 2
• Presence of urinary tract symptoms (if ascertainable) or signs of UTI should guide the decision to investigate the urinary tract as a potential source of fever 1
• Non-specific symptoms like low-grade fever, confusion, or functional decline alone are not reliable indicators of UTI and should not trigger urinalysis or urine culture 2

Recommended Urine Investigations

Urinalysis First Approach

• The minimum laboratory evaluation for suspected UTI should include urinalysis for determination of leukocyte esterase and nitrite level by dipstick and microscopic examination for WBCs 1, 3
• Pyuria is defined as ≥10 WBCs/high-power field or a positive leukocyte esterase test 3, 4
• Only if pyuria is present should a urine culture with antimicrobial susceptibility testing be ordered 1, 2

Specimen Collection

• For patients with indwelling urinary catheters, the catheter should be replaced prior to specimen collection and institution of antibiotic therapy 1, 3
• For non-catheterized patients, appropriately collected urine specimens are essential for accurate diagnosis 1
• In-and-out catheterization may be necessary for proper specimen collection in patients unable to provide a clean-catch specimen 1

Special Considerations for Suspected Urosepsis

• If urosepsis is suspected (fever, shaking chills, hypotension, or delirium), urine and paired blood specimens should be obtained for culture and antimicrobial susceptibility testing 1, 3
• A Gram stain of uncentrifuged urine should be requested when urosepsis is suspected 1, 3
• Complete blood count with differential should be performed, with attention to elevated WBC count (≥14,000 cells/mm³) and left shift (percentage of band neutrophils ≥16% or total band count ≥1,500 cells/mm³) 3

Interpretation of Results

• Asymptomatic bacteriuria is common, particularly in older adults and those with indwelling catheters, and does not require treatment 2, 5
• In patients with chronic indwelling catheters, bacteriuria and pyuria are virtually universal and not indicative of infection without accompanying symptoms 2
• Nitrites are likely more sensitive and specific than other dipstick components for UTI, particularly in the elderly 5
• Positive dipstick testing increases the probability of UTI but should be interpreted in context of the patient's symptoms 5

Common Pitfalls to Avoid

• Avoid ordering urine cultures for asymptomatic patients or those with only non-specific symptoms 1, 2
• Do not treat based solely on positive urine culture without considering clinical symptoms 2, 4
• Avoid attributing persistent fever to UTI without specific urinary symptoms or positive urinalysis 2
• Remember that treating asymptomatic bacteriuria leads to unnecessary antibiotic use, increased resistance, and potential harm 2, 6

Algorithm for Urine Testing in Patients with HAP and Persistent Fever

1. Assess for specific urinary symptoms (dysuria, frequency, urgency, suprapubic pain) 1, 2
2. If urinary symptoms present OR suspected urosepsis, perform urinalysis 1, 3
3. If pyuria present on urinalysis, replace catheter (if present) and obtain urine culture 1
4. If urosepsis suspected, also obtain blood cultures and consider Gram stain of urine 1, 3
5. If no urinary symptoms and no signs of urosepsis, focus on other potential sources of fever 1, 2