Can nitrates (nitrogen-containing compounds) in urine cause a false positive result for glucose in a urinalysis?

Nitrates in Urinalysis Do Not Cause False Positive Glucose Results

No, nitrates in urine do not cause false positive glucose results in urinalysis. The presence of nitrates in urine is not documented as an interfering substance for glucose testing in urinalysis.

Understanding Urinalysis Glucose Testing Methods

• Urinalysis glucose testing is typically performed using glucose oxidase (GO) or glucose dehydrogenase (GDH) based methods 1
• These enzymatic methods have largely replaced older copper-reduction methods for detecting glucose in urine 1
• Different glucose testing methodologies have specific interference patterns that do not include nitrates 1

Known Interfering Substances for Glucose Testing

Substances causing false positive glucose results:

• Air exposure of test strips can cause false positive glucose readings (trace to 1+) 2
• For older copper-reduction methods (less commonly used today), strong reducing substances can cause false positives 3

Substances causing false negative glucose results:

• Ascorbic acid (vitamin C) in high doses 3, 1
• Sodium fluoride (sometimes used as a preservative) with glucose oxidase strips 4
• Beta-lactam antibiotics, levodopa, and salicylates with certain testing methods 3
• Prolonged air exposure of test strips can affect accuracy 2

Nitrates in Urinalysis

• Nitrates in urine are primarily used as an indicator of bacterial urinary tract infections 1
• Nitrite testing has high specificity (99%) but lower sensitivity (39-49%) for detecting UTIs 1
• While nitrates themselves don't interfere with glucose testing, bacterial infections that produce nitrates may cause other metabolic changes 5

Potential Confounding Factors in Urinalysis

• Collection technique can significantly impact urinalysis results, with "non-clean" collection showing higher rates of abnormal findings across multiple parameters 5
• Urinalysis indices are often abnormal even in disease-free populations using ideal collection techniques 5
• Multiple positive parameters on urinalysis should be interpreted in clinical context rather than in isolation 1

Clinical Implications

• When evaluating unexpected glucose results in urinalysis, consider:

  • Specimen collection technique 5
  • Medication use, particularly those known to interfere with glucose testing 3
  • Test strip exposure to air or improper storage 2
  • The specific glucose testing methodology used by the laboratory 1

• For accurate glucose monitoring in patients with diabetes, self-monitoring of blood glucose (SMBG) is preferred over urine glucose testing due to the limitations of urine testing 1

• In patients with advanced kidney disease, be aware that various factors can affect glucose readings, but nitrates are not among the documented interfering substances 1