What protein is detected by a urine dipstick when assessing proteinuria?

• A. Albumin
• B. Globulins
• C. Myoglobin
• D. Bence Jones protein

Answer: (A)

The test on a urine dipstick is designed to detect mainly albumin. The dipstick uses a protein-binding dye that changes color when albumin binds to it, so it responds most strongly to albumin at the concentrations typically seen in early or glomerular proteinuria. Other urinary proteins—globulins, myoglobin, and Bence Jones (light) chains—do not interact as reliably with that dye, so the dipstick is far less sensitive to them. In practice, a positive dipstick largely reflects albuminuria, while non-albumin proteins may be missed or only poorly detected, which is why further testing (like albumin-to-creatinine ratio or specific protein studies) is sometimes needed to characterize the proteinuria.