Does This Urinalysis Indicate a Urinary Tract Infection?
Yes, this urinalysis strongly suggests a urinary tract infection based on the markedly elevated white blood cells (50-100/hpf) combined with the presence of bacteria, despite negative leukocyte esterase and nitrite results.
Key Urinalysis Findings Analysis
The most critical findings pointing toward UTI are:
- WBC count of 50-100/hpf (normal 0-2/hpf): This represents significant pyuria, which is the hallmark of UTI when combined with bacteriuria 1, 2
- Bacteria present (Few): Even "few" bacteria on microscopy in the presence of significant pyuria suggests infection rather than contamination 1
- RBC 2-5/hpf (mildly elevated): Consistent with inflammatory changes in the urinary tract 2
Understanding the Discordant Results
The negative leukocyte esterase result appears contradictory to the high WBC count, but this represents a false-negative leukocyte esterase test. This can occur due to:
- High specific gravity (1.028): Concentrated urine can interfere with the chemical reaction of leukocyte esterase 2
- Acidic pH (6.0): May reduce test sensitivity 2
- Certain medications or urinary constituents: Can cause false-negative results 2
The negative nitrite test has limited value here because nitrite testing has poor sensitivity (19-48%) and is frequently negative in true UTIs, particularly when bladder dwell time is short or with non-nitrate-reducing organisms 2, 3
Diagnostic Interpretation
The microscopic examination supersedes the dipstick results. The American Academy of Pediatrics guidelines emphasize that the diagnosis of UTI requires both pyuria (≥10 WBCs/hpf) and bacteriuria 1. This specimen clearly meets both criteria with 50-100 WBCs/hpf.
The combination of findings yields:
- Microscopic WBCs of 50-100/hpf: Interval likelihood ratio of 47.50, dramatically increasing UTI probability 3
- Bacteria present: Further supports infection over contamination 2
Specimen Quality Considerations
The extremely turbid clarity and trace protein are consistent with the high WBC count and support an inflammatory process 2. However, the specimen quality appears adequate for interpretation—there is no mention of excessive epithelial cells that would suggest contamination 2.
Clinical Action Required
You must obtain a urine culture before initiating antibiotics to:
- Confirm the diagnosis definitively 4, 5
- Identify the causative organism 4
- Guide antibiotic selection based on susceptibilities 4, 5
The negative leukocyte esterase with high microscopic WBCs suggests a non-E. coli organism is more likely (likelihood ratio 0.4 for E. coli when leukocyte esterase is negative) 6. Non-E. coli organisms may show different antibiotic susceptibility patterns, making culture results particularly important 6.
Common Pitfall to Avoid
Do not dismiss this as "negative UA" based solely on the dipstick results. The microscopic examination showing 50-100 WBCs/hpf with bacteria is diagnostic of pyuria and bacteriuria regardless of negative leukocyte esterase and nitrite 1, 2. Relying only on dipstick results would miss this UTI and delay appropriate treatment 2.