Which substance in urine contributes to the specimen's specific gravity when present?

Which substance in urine contributes to the specimen's specific gravity when present?

• A. 50-100 RBC/hpf
• B. 85 mg/dL glucose
• C. 3+ amorphous phosphates
• D. Moderate bacteria

Answer: (B)

Specific gravity reflects how dense urine is due to dissolved solutes in the fluid. Glucose in urine is a dissolved solute, so when it’s present at levels like 85 mg/dL it adds particles to the urine solution and increases its density relative to water. That makes glucose a contributor to higher specific gravity. The other items are not dissolved solutes. Red blood cells and bacteria are cellular material suspended in the urine and don’t significantly change the dissolved particle concentration. Amorphous phosphates are crystals that may affect clarity or turbidity but not the dissolved solute content that determines density. Therefore they don’t meaningfully raise the specific gravity.

Specific gravity reflects how dense urine is due to dissolved solutes in the fluid. Glucose in urine is a dissolved solute, so when it’s present at levels like 85 mg/dL it adds particles to the urine solution and increases its density relative to water. That makes glucose a contributor to higher specific gravity.

The other items are not dissolved solutes. Red blood cells and bacteria are cellular material suspended in the urine and don’t significantly change the dissolved particle concentration. Amorphous phosphates are crystals that may affect clarity or turbidity but not the dissolved solute content that determines density. Therefore they don’t meaningfully raise the specific gravity.