II. Mechanism
- Some Bacteria (E. coli, Klebsiella, Proteus) reduce urine nitrates to nitrites
- Many other Bacteria do NOT reduce urine nitrates (e.g. Enterococcus, Pseudomonas, Acinetobacter)
- Nitrite production typically requires urine standing (in Bladder) for at least 4 to 6 hours
- Infants do not hold their urine, and do not typically demonstrate nitrite on the urine sample
III. Efficacy
- Test Specificity: >91%
- Test Sensitivity: <49%
IV. Interpretation
- Normal: Negative
- Positive
V. Causes: False Positive nitrite on Urinalysis
- Vaginal contaminant
- Phenazopyridine
- Dipstick exposed to air
- Close test strip containers immediately
- Strip exposed to air for 1 week: 33% False Positive
- Strip exposed to air for 2 weeks: 75% False Positive
VI. Causes: False Negative Urine Nitrite
- Increased Urine Specific Gravity
- Increased Urobilinogen
- Bacteria lacking nitrate reductase enzyme (e.g. Enterococcus)
- Urine pH <6.0
- Vitamin C supplementation
- Low nitrate diet
- Short Bladder incubation time (<4 hours)