What does a urinalysis showing negative nitrates, mild proteinuria, leukocyturia (White Blood Cells (WBC)), hematuria (Red Blood Cells (RBC)), and few epithelial cells indicate, and should I be concerned?

Urinalysis Interpretation and Management Recommendations

Direct Answer

This urinalysis shows pyuria (10-25 WBC/hpf) and hematuria (15-30 RBC/hpf) with negative nitrites, which is concerning for a urinary tract infection (UTI) and warrants obtaining a urine culture before making treatment decisions. The negative nitrite result does not rule out UTI, as nitrites have only 49-53% sensitivity despite 98-99% specificity 1, 2.

What This Urinalysis Is Telling You

Pyuria (WBC 10-25/hpf)

• This level of pyuria is significant and suggests urinary tract inflammation or infection 1
• WBC counts of 10-25/hpf have a likelihood ratio of approximately 18-19 for UTI when >20/hpf, and LR of 2.8 when 6-10/hpf 1
• Pyuria ≥5 WBC/hpf is considered positive for UTI screening in most guidelines 1

Negative Nitrites

• The negative nitrite does NOT exclude UTI - nitrites have poor sensitivity (39-53%) but excellent specificity (98-99%) 1, 2
• Nitrite formation requires bacteria to convert dietary nitrates, which takes approximately 4 hours of bladder incubation time 3
• Patients who void frequently (including young children) may have negative nitrites despite true infection 1
• Non-E. coli organisms (Enterococcus, Klebsiella, Pseudomonas) often do not produce nitrites 4, 5

Hematuria (15-30 RBC/hpf)

• Mild hematuria can occur with UTI but is nonspecific 6
• The combination of pyuria + hematuria increases concern for UTI 7

Minimal Epithelial Cells (2-5)

• Low epithelial cell count suggests the specimen is not heavily contaminated 1
• Specimens with >10 epithelial cells should be considered contaminated 1

Trace Protein

• Mild proteinuria is common with UTI due to inflammation 6
• Not specific but supports inflammatory process 7

Should You Be Concerned?

Yes, you should be concerned. This urinalysis pattern (pyuria with negative nitrites) represents a common scenario where UTI is still likely:

• 30% of children with culture-proven UTI have negative urinalysis (defined as negative leukocyte esterase, negative nitrites, and WBC <5/hpf) 1
• 10-50% of patients with documented UTI can have false-negative urinalysis results 1
• 20% of febrile infants with pyelonephritis lack pyuria on initial urinalysis, though your patient has pyuria present 1
• The presence of pyuria (10-25 WBC/hpf) is the most important finding and indicates urinary tract inflammation requiring further evaluation 1, 8

Should You Treat This Patient?

Immediate Management Algorithm

Step 1: Obtain a urine culture BEFORE starting antibiotics 1, 2

• The diagnosis of UTI requires BOTH urinalysis evidence (pyuria/bacteriuria) AND positive culture with ≥50,000 CFU/mL 1, 2
• Once antibiotics are started, the opportunity for definitive diagnosis is lost 1

Step 2: Assess clinical severity

If patient appears ill, toxic, or has high fever/systemic symptoms:

• Start empiric antibiotics immediately after obtaining culture 1
• Do not delay treatment waiting for culture results 1

If patient is well-appearing with mild symptoms:

• You may monitor clinically while awaiting culture results 1
• Ensure reliable follow-up is available 1

Step 3: Consider collection method

• If specimen was obtained by bag collection, a positive result requires confirmation by catheterization or suprapubic aspiration 1
• Bag specimens have 70% specificity, meaning 85% of positive bag results are false positives 1
• A catheterized specimen has 95% sensitivity and 99% specificity 1

Treatment Considerations Based on Patient Age

For children <2 years with fever:

• Urine culture is mandatory even with negative urinalysis 1
• Urinalysis alone cannot rule out UTI in this age group 1
• Consider empiric treatment if clinically indicated while awaiting culture 1

For older children and adults:

• Clinical symptoms (dysuria, frequency, urgency, suprapubic pain) guide treatment decisions 3
• Symptomatic patients with pyuria can be treated empirically while awaiting culture 6, 8

Empiric Antibiotic Selection (if treatment indicated)

The negative nitrite suggests possible non-E. coli organism 5:

• Negative UA with positive culture is more likely non-E. coli (59% vs 41% E. coli) 5
• Non-E. coli organisms (Klebsiella, Enterococcus) are less likely to cause pyuria and nitrite positivity 4, 5

First-line empiric options:

• Nitrofurantoin 100mg twice daily for 5-7 days (if CrCl ≥30 mL/min) 3
• Trimethoprim-sulfamethoxazole may be more effective for non-E. coli organisms (82.2% sensitive in negative UA group) 5
• Cefazolin or cefuroxime for suspected E. coli (94-98% sensitive) 5

Critical Pitfalls to Avoid

1. Do not rule out UTI based solely on negative nitrites - this would miss 47-61% of true infections 1, 2

2. Do not treat based on urinalysis alone without culture - you need culture confirmation to distinguish true UTI from asymptomatic bacteriuria 1

3. Do not ignore pyuria - the presence of 10-25 WBC/hpf is the most important finding and indicates inflammation requiring investigation 1, 8

4. Do not accept bag-collected specimens for definitive diagnosis - positive results require catheterized confirmation 1, 2

5. Do not treat asymptomatic bacteriuria - treatment requires both positive culture AND evidence of pyuria/symptoms 1, 3

Bottom Line Management

For this specific urinalysis (WBC 10-25, negative nitrites, RBC 15-30, minimal epithelial cells):

• Obtain urine culture immediately 1, 2
• If patient is symptomatic or appears ill, start empiric antibiotics after culture obtained 1, 3
• If patient is well-appearing, you may observe clinically with close follow-up 1
• Adjust antibiotics based on culture results and sensitivities 3, 5
• Ensure specimen was properly collected (catheterized if bag specimen positive) 1