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Nitrite (Urine) Medical Background

	Overview Medical Background Literature

Medical Background

Source & biological action

Usually urine does not contain any nitrite; it is only formed in case of a bacterial urinary tract infection. Most gram-negative uropathogenic bacteria possess nitrate reductase that converts nitrate from dietary metabolites into nitrite.

Indications for testing

• Suspicion of bacterial urinary tract infection
• Pregnancy

Patient preparation

• Collection of morning midstream urine specimen (the residence time of the urine in the bladder should be at least 4 to 6 hours)
• Careful anogenital hygiene preceding urine collection
• Ingestion of vegetables on the preceding day (contain nitrate!)

Determination

Using the Combur-Test® urine test strips, nitrite can rapidly and reliably be determined in the primary care setting. For efficient and standardized urine testing in your office use the Urisys 1100 analyzer.

Results

Reference range

Normal	Nitrite is not detectable
Bacteriuria (> 105 organism/ml)	A red dye appears

The practical detection limit of nitrite is 0.05 mg/dl (11 µmol/l).

Interpretation

Conditions with nitrite in the urine

• Bacterial urinary tract infections
• Manipulation of specimen (drug abuse)

Tips & recommendations

• Main risk factors for urinary tract infections are sexual intercourse, use of diaphragms, enlarged prostate, urolithiasis, diabetes, bladder catheters, anatomic abnormalities, and old age.
• About 50 percent of bacterial urinary tract infections can be identified by detection of nitrite with Combur-Test® urine test strips. The recognition rate can be increased up to 90 percent if the collection of urine is performed correctly.
• A single negative test does not exclude a urinary infection because some common pathogenic bacteria, e.g. Enterococcus sp., or Staphylococcus sp. lack nitrate reductase.
• Positive nitrite tests: Confirm the diagnosis of a bacterial urinary tract infection with a determination of leukocytes, bacteria count, and microbial species.
• Treat urinary tract infections promptly and properly to avoid serious complications such as kidney infections.

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