Nitrites in Urine
Análisis de orinaÚltima revisión: 7 de abril de 2026. Enfoque de fuentes: contexto estándar de interpretación de laboratorio, material médico de referencia y orientación clínica o de salud pública cuando corresponde.
¿Qué es Nitrites in Urine?
The nitrite test on a urine dipstick detects the presence of nitrites, which are produced when certain bacteria convert dietary nitrates (naturally present in urine) into nitrites through an enzymatic process. This conversion is performed by gram-negative bacteria, most commonly Escherichia coli, Klebsiella, and Proteus species—organisms that are responsible for the majority of urinary tract infections. A positive nitrite test therefore serves as a chemical indicator of bacterial infection in the urinary tract.
The nitrite test is one of the most specific indicators of a UTI on a standard urinalysis dipstick, with a specificity of approximately 95–98%. However, its sensitivity is lower, around 45–60%, meaning that a negative result does not rule out infection. This is because not all bacteria produce nitrites—gram-positive organisms like Enterococcus and Staphylococcus saprophyticus lack the enzyme needed for nitrate-to-nitrite conversion. Additionally, the bacteria need sufficient time in the bladder (typically 4 or more hours) to produce detectable nitrite levels, which is why a first-morning urine specimen provides the most reliable results.
Por qué importa
A positive nitrite test is a highly reliable indicator that bacteria capable of causing a UTI are present in the urinary tract. When combined with a positive leukocyte esterase result, the predictive value for UTI exceeds 90%, allowing clinicians to begin empiric antibiotic treatment before culture results are available—which typically takes 24–48 hours. This rapid diagnosis is particularly valuable in settings like emergency departments and urgent care clinics where timely treatment prevents the progression of lower UTIs to more serious kidney infections. The test is also an inexpensive screening tool used in prenatal care to detect asymptomatic bacteriuria.
Rangos de referencia normales
| Grupo | Rango | Unidad |
|---|---|---|
| Normal | Negative | |
| Positive | Any positive result is abnormal |
Los rangos de referencia pueden variar entre laboratorios. Compara siempre tus resultados con los rangos proporcionados por tu laboratorio.
Qué significan los niveles altos de Nit
Causas comunes
- Urinary tract infection with gram-negative bacteria
- Asymptomatic bacteriuria
- Kidney infection (pyelonephritis)
- Catheter-associated UTI
- Contaminated or improperly stored urine sample
Posibles síntomas
- Burning or painful urination
- Increased frequency and urgency of urination
- Cloudy or strong-smelling urine
- Lower abdominal or pelvic pain
- Fever and flank pain (kidney infection)
- May be completely asymptomatic
Qué hacer: A positive nitrite test strongly suggests a bacterial UTI and typically warrants antibiotic treatment. Your doctor should order a urine culture with sensitivity testing to identify the specific organism and confirm the most effective antibiotic. Begin empiric antibiotics while awaiting culture results if symptoms are present. Increase fluid intake and complete the full course of prescribed antibiotics. Follow up with a repeat urinalysis if symptoms do not resolve within 48–72 hours of starting treatment.
Qué significan los niveles bajos de Nit
Causas comunes
- No significant bacterial infection present
- Infection with organisms that do not convert nitrate to nitrite
- Urine not in bladder long enough for conversion (recent frequent voiding)
- Low dietary nitrate intake
Posibles síntomas
- No symptoms—a negative nitrite test is normal
Qué hacer: A negative nitrite test is a normal finding. However, remember that a negative result does not completely exclude a UTI, especially if symptoms are present. If you have UTI symptoms with a negative nitrite test, your doctor may still order a urine culture or treat based on other findings such as positive leukocyte esterase or bacteria on microscopy.
¿Cuándo se recomienda la prueba de Nit?
- When symptoms of a urinary tract infection are present
- As part of routine urinalysis screening
- During prenatal visits to screen for asymptomatic bacteriuria
- When monitoring response to UTI treatment
- In patients with recurrent UTIs
- When evaluating fever of unknown origin
Preguntas frecuentes
Biomarcadores relacionados
Referencias y enfoque de revisión
Las páginas del glosario de biomarcadores son explicaciones educativas y deben interpretarse junto con los rangos de referencia y comentarios proporcionados por tu laboratorio y tu profesional de salud. Para conocer nuestros estándares editoriales y proceso de revisión, consulta nuestra Política editorial y nuestro Proceso de revisión de contenido.
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Subir resultados de laboratorio →Aviso médico: Esta información es solo educativa y no sustituye el consejo, diagnóstico ni tratamiento médico profesional. Los rangos de referencia pueden variar entre laboratorios. Consulta siempre a tu profesional sanitario para interpretar tus resultados concretos.