From the Guidelines
The presence of leukocytes in a urinalysis (UA) is indicative of an inflammatory response in the urinary tract, which may be due to various causes, including infection, and is not exclusive to urinary tract infections (UTIs) 1.
Key Findings
- The diagnostic value of UA for UTI is limited, and the positive predictive value of pyuria for diagnosing infection is low, as it can also indicate genitourinary inflammation due to noninfectious reasons 1.
- A UA can help rule out infection in most patient populations if pyuria is absent, but clinical symptoms should be the primary basis for diagnosing UTI, with UA findings used as supplementary information 1.
- In cases where leukocytes are accompanied by other abnormal findings, such as nitrites or blood, a course of antibiotic therapy may be initiated, typically with fluoroquinolones or cephalosporins, which are recommended for oral empiric treatment of uncomplicated pyelonephritis 1.
Treatment Considerations
- For patients with uncomplicated pyelonephritis, a short outpatient course of antibiotic treatment can be equivalent to longer therapy durations in terms of clinical and microbiological success, but may be associated with a higher recurrence rate 1.
- Patients with complicated pyelonephritis or those requiring hospitalization should be treated initially with an intravenous antimicrobial regimen, such as a fluoroquinolone, an aminoglycoside, or an extended-spectrum cephalosporin or penicillin 1.
- The choice of antibiotic therapy should be based on local resistance patterns and optimized to ensure effective treatment 1.
From the Research
Presence of Leukocytes in Urinalysis
The presence of leukocytes (white blood cells) in urinalysis (UA) is a significant indicator of urinary tract infection (UTI) or inflammation.
- A value of > or = 10 WBC/mm3 is significant for bacteriuria, as determined by a hemocytometer 2.
- Manual microscopy studies show that > or = 8 WBC/high-power field reliably predicts a positive urine culture 2.
- Automated urinalysis provides more sensitive detection of leukocytes and bacteria in the urine, with a value of > 2 WBC/hpf being significant pyuria indicative of inflammation of the urinary tract 2.
Diagnostic Performance of Urinalysis
The diagnostic performance of urinalysis for detecting UTI can be affected by various factors, including urine concentration.
- The positive likelihood ratios for the presence of leukocyte esterase and microscopic pyuria decrease with increasing specific gravity, indicating that the diagnostic performance of urinalysis varies by urine concentration 3.
- The presence of leukocyte esterase and pyuria can predict UTI, but the accuracy of these predictions can be influenced by the urine concentration and other factors 3, 4.
Prediction of Causative Agent and Antibiotic Sensitivities
Urinalysis can provide some information about the causative agent and antibiotic sensitivities, but its accuracy is limited.
- A positive urinalysis result is more likely to be associated with Escherichia coli (E. coli) infection, while a negative result may indicate a non-E. coli organism 4.
- The likelihood ratio of positive leukocyte esterase, positive nitrites, and urine white blood cell count can predict E. coli versus non-E. coli infections, but the accuracy of these predictions is not high 4.
- Antibiotic sensitivity patterns can vary between E. coli and non-E. coli groups, and urinalysis results can provide some guidance on empiric antibiotic selection 4.