Urinalysis with Reflex to Culture and Sensitivity is Superior to Direct Culture and Sensitivity for Suspected UTIs
For suspected urinary tract infections, urinalysis with reflex to culture and sensitivity is better than directly ordering culture and sensitivity as it reduces unnecessary cultures, improves antimicrobial stewardship, and maintains diagnostic accuracy. 1
Diagnostic Approach for Suspected UTIs
- Urinalysis should be performed first as a screening test before proceeding to urine culture for patients with suspected UTI 2, 3
- Urinalysis includes testing for leukocyte esterase and nitrite by dipstick and microscopic examination for WBCs 2
- Leukocyte esterase has higher sensitivity (83-94%) but lower specificity (78-91%) compared to nitrite testing, which has higher specificity (98%) but lower sensitivity (53%) for detecting UTIs 3
- The absence of pyuria has excellent negative predictive value and can effectively rule out UTI 4
Benefits of Urinalysis with Reflex to Culture
- Urine culture should only be ordered if pyuria (≥10 WBCs/high-power field) or positive leukocyte esterase/nitrite test is present on urinalysis 2, 5
- Reflex urine culturing resulted in a 46.6% reduction in urine culture ordering in one study and a 39.5% reduction in UTI antibiotic days of therapy in another 1, 6
- Conditional reflex urine culturing decreases both the number of urine cultures ordered (22.8% immediate reduction) and performed (38.9% immediate reduction) 1
- This approach prevents unnecessary antibiotic treatment of asymptomatic bacteriuria 7
When Direct Culture and Sensitivity May Be Appropriate
- In patients with suspected urosepsis (fever, shaking chills, hypotension, or delirium), both urine and paired blood specimens should be obtained for culture 2, 5
- For residents with long-term indwelling urethral catheters and suspected urosepsis, catheters should be changed prior to specimen collection and antibiotic therapy 2, 5
- In noncatheterized residents, diagnostic evaluation for UTI should be reserved for those with acute onset of UTI-associated symptoms (fever, dysuria, gross hematuria, new or worsening urinary incontinence) 2
Special Population Considerations
- For children younger than 2 years with suspected UTI, a urine culture should be obtained in conjunction with urinalysis because a negative urinalysis does not always exclude UTI 2
- In patients with chronic indwelling catheters, bacteriuria and pyuria are virtually universal and not indicative of infection without accompanying symptoms 5, 8
- For elderly patients, non-specific symptoms like confusion, falls, or functional decline alone should not trigger antibiotic treatment for presumed UTI 3, 4, 5
Common Pitfalls to Avoid
- Ordering urine cultures for asymptomatic patients leads to unnecessary antibiotic use and contributes to antimicrobial resistance 2, 3, 4
- Treating based solely on positive urine culture without considering clinical symptoms leads to overtreatment 4, 5
- Bag specimens have high contamination rates (26%) compared to catheterization (12%) or suprapubic aspiration (1%) 3
- In patients with chronic indwelling catheters, neither urinalysis nor urine culture appears to be a reliable test for symptomatic UTIs 8
Proper Specimen Collection
- Appropriately collected urine specimens include a mid-stream or clean-catch specimen from cooperative and functionally capable patients 2
- For women who cannot provide a clean-catch specimen, in-and-out catheterization may be necessary 2
- For men who cannot provide a clean-catch specimen, a freshly applied, clean condom external collection system with frequent monitoring of the urine bag may be used 2
- If urosepsis is suspected, urine and paired blood specimens should be obtained for culture and antimicrobial susceptibility testing 2