If a specimen is contaminated with 10% of a solution containing 5% dextrose, the measured glucose will increase by at least how much?

If a specimen is contaminated with 10% of a solution containing 5% dextrose, the measured glucose will increase by at least how much?

• A. 100 mg/dL or more
• B. 300 mg/dL or more
• C. 500 mg/dL or more
• D. 1000 mg/dL or more

Answer: (C)

The key idea is converting percent concentrations to an absolute glucose amount in mg/dL when a portion of the sample is replaced by a dextrose solution. A 5% dextrose solution has 5 g of glucose per 100 mL. If 10% of the specimen’s volume is this solution, the final mixture contains 0.10 × 5 g = 0.5 g of glucose per 100 mL, which equals 500 mg/dL. Therefore, the measured glucose will increase by at least 500 mg/dL due to the contamination, on top of whatever glucose was already present.

The key idea is converting percent concentrations to an absolute glucose amount in mg/dL when a portion of the sample is replaced by a dextrose solution.

A 5% dextrose solution has 5 g of glucose per 100 mL. If 10% of the specimen’s volume is this solution, the final mixture contains 0.10 × 5 g = 0.5 g of glucose per 100 mL, which equals 500 mg/dL. Therefore, the measured glucose will increase by at least 500 mg/dL due to the contamination, on top of whatever glucose was already present.