Nitrites — Normal Range & Interpretation
Urine nitrites detect bacterial conversion of dietary nitrates to nitrites in the bladder. A positive result signals bacteriuria from gram-negative organisms that express nitrate reductase, most notably Escherichia coli, Klebsiella, and Proteus. Nitrites support the diagnosis of urinary tract infection when paired with leukocyte esterase, pyuria, and clinical symptoms such as dysuria, frequency, and urgency.
| Male | Female | Unit | Category |
|---|---|---|---|
| Negative | Negative | — | Urinalysis |
Clinical Context
Urine nitrites detect bacterial conversion of dietary nitrates to nitrites in the bladder. A positive result signals bacteriuria from gram-negative organisms that express nitrate reductase, most notably Escherichia coli, Klebsiella, and Proteus. Nitrites support the diagnosis of urinary tract infection when paired with leukocyte esterase, pyuria, and clinical symptoms such as dysuria, frequency, and urgency.
A positive nitrite result points to gram-negative bacteriuria and guides empiric antibiotic selection for cystitis and pyelonephritis in adults. A negative result does not rule out infection. Gram-positive pathogens like Enterococcus and Staphylococcus saprophyticus lack nitrate reductase and produce false negatives, as does dilute urine, low dietary nitrate intake, frequent voiding that shortens bladder dwell time below four hours, and vitamin C interference. False positives arise from contaminated specimens and improper strip storage.
High-yield for NP boards: the classic UTI urinalysis pattern — positive nitrites plus positive leukocyte esterase in a symptomatic patient. Expect questions linking nitrites to E. coli as the predominant uropathogen, scenarios where nitrites remain negative despite infection with Enterococcus or S. saprophyticus, and cases requiring urine culture to confirm the organism. Candidates must also distinguish asymptomatic bacteriuria from true UTI and identify pregnancy as an indication to treat.
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