The colorimetric reagent strip test for protein is able to detect as little as 5-20 mg of protein per deciliter. What may cause a false-positive urine protein reading?

The colorimetric reagent strip test for protein is able to detect as little as 5-20 mg of protein per deciliter. What may cause a false-positive urine protein reading?

• A. Uric acid concentration is greater than 0.5 g/day.
• B. Vitamin C concentration is greater than 0.5 g/day.
• C. Glucose concentration is greater than 130 mg/day.
• D. pH is greater than 8.0.

Answer: (D)

The test detects protein with a color change on a pad that responds to protein presence, but can be influenced by urine pH. When the urine is strongly alkaline (pH > 8.0), the indicator can change color even without real protein, leading to a false-positive reading. This interference happens because the dye and chemical reactions on the pad become unstable or misrepresent the amount of protein in highly basic urine. The other factors listed do not reliably cause a false-positive result: high uric acid or glucose don’t consistently trigger the pad in the absence of protein, and high vitamin C tends to cause false negatives by masking the true color change rather than creating a false-positive signal.

The test detects protein with a color change on a pad that responds to protein presence, but can be influenced by urine pH. When the urine is strongly alkaline (pH > 8.0), the indicator can change color even without real protein, leading to a false-positive reading. This interference happens because the dye and chemical reactions on the pad become unstable or misrepresent the amount of protein in highly basic urine. The other factors listed do not reliably cause a false-positive result: high uric acid or glucose don’t consistently trigger the pad in the absence of protein, and high vitamin C tends to cause false negatives by masking the true color change rather than creating a false-positive signal.