Bacterial Infection Indicator
Certain bacteria (especially E. coli and other Gram-negative organisms) convert dietary nitrates into nitrites. Finding nitrites in urine is strong evidence of bacterial UTI. But not all bacteria produce nitrites (Enterococcus, Staphylococcus don't), so a negative nitrite test doesn't rule out UTI.
What is Urine Nitrites?
Dipstick detects nitrites produced by bacterial reduction of urinary nitrates. Requires: (1) bacteria that produce nitrite reductase (Gram-negatives, especially E. coli), (2) sufficient bladder dwell time (first-morning specimen is best), (3) dietary nitrate intake.
↑ What High Urine Nitrites Means
Strong evidence of bacterial UTI. Nitrite-positive urine has very high specificity (~95%) for UTI, but sensitivity is only ~50% (many UTIs are nitrite-negative).
Common symptoms:
Dysuria, frequency, urgency, suprapubic discomfort · Cloudy or foul-smelling urine · If pyelonephritis: fever, flank pain, nausea
↓ What Low Urine Nitrites Means
N/A.
Common symptoms:
N/A
Why It Matters
When normal:
Very specific for UTI (~95%)
Combined with leukocyte esterase: good UTI screening
Rapid point-of-care result
Risks if abnormal:
Sensitivity only ~50%—negative doesn't exclude UTI
Gram-positive bacteria (Enterococcus, Staph) don't produce nitrites
Requires adequate bladder dwell time (frequent voiding → false negative)
What Can Cause Abnormal Levels?
Urinary Tract Infection (Gram-negative)
85% likelyE. coli (most common UTI pathogen) and other Gram-negatives convert nitrate to nitrite.
Contamination
Bacterial contamination of specimen can cause false positive.
Specimen Handling
Prolonged room temperature storage allows bacterial growth and nitrite production.
What You Can Do
Nitrite + leukocyte esterase positive + symptoms = treat as UTI
Impact: Start empiric antibiotics pending culture \u00B7 Timeline: Same day
Send urine culture for confirmation and sensitivities
Impact: Guides targeted antibiotic therapy \u00B7 Timeline: Before antibiotics ideally
If lifestyle changes aren't enough:
Use first-morning specimen for best sensitivity
Impact: Longer bladder dwell time allows more nitrite production \u00B7 Timeline: At collection
Recommended retest: Post-treatment urinalysis to confirm clearance if indicated
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