Proteinuria, or the presence of excess protein in the urine, can be an indicator of various health conditions, particularly kidney disease.
Among the methods to detect proteinuria, the urine test strip (dipstick) method is one of the most commonly used qualitative tests due to its simplicity and cost-effectiveness.
Here’s a detailed guide to using and interpreting urine test strips.
What is a Urine Test Strip?
Urine test strips are thin plastic strips embedded with pads containing chemical reagents. These reagents react with specific components in the urine, causing a color change. The test strip can evaluate various parameters, such as:
- pH: Measures urine acidity.
- Protein: Detects albumin (the main protein in urine).
- Glucose: Indicates sugar levels.
- Ketones: Signals fat metabolism.
- Bilirubin: Reflects liver function.
- Red blood cells: Indicates hematuria.
- White blood cells: Suggests infection.
- Nitrites: Points to bacterial infections.
Key Note: We primarily designed urine strip to detect albumin and it may not identify other proteins like tubular proteins or immunoglobulin light chains.
How to Use a Urine Test Strip
- Prepare the Sample: Collect fresh urine in a clean container.
- Dip the Strip: Immerse the test strip briefly (1-2 seconds) in the urine sample.
- Remove and Wait: Allow the strip to rest for the specified time, as indicated in the manufacturer’s instructions (usually 30-60 seconds).
- Compare Colors: Match the color changes on the strip to the provided chart to interpret the results.
Interpreting Proteinuria on a Urine Test Strip
- Negative: No detectable protein.
- Trace: Possible physiological proteinuria or early-stage kidney issues.
- + to ++++: Indicates increasing levels of proteinuria, suggesting potential kidney damage or disease.
Important Considerations:
- False Positives: Can occur due to concentrated urine, alkaline pH, contamination.
- False Negatives: Can happen with dilute urine or when protein levels are below the test’s detection threshold (e.g., microalbuminuria).
Limitations of Urine Test Strips
- Detection Threshold: Urine test strips may not detect albumin levels below 0.25–0.3 g/L.
- Specificity: It cannot identify other proteins in the urine.
- Environmental Factors: High or low urine pH, specific gravity, interfering substances (e.g., Vitamin C) can affect accuracy.
For more accurate quantification, additional tests like a urine albumin-to-creatinine ratio (ACR) or 24-hour urine protein analysis may be required.
Cost and Accessibility
Urine test strips are affordable, with a pack of 50–100 strips costing approximately $10–30. They are widely available in pharmacies. However, professional interpretation of results may require consulting a healthcare provider.
Proteinuria Definition (According to KDIGO Guidelines)
- Adults: Protein levels exceeding 150 mg per 24 hours are abnormal.
- Children: Levels above 140 mg/m² per 24 hours are abnormal (adjusted based on age).