Identification of which of the following is useful in the early stages of glomerular dysfunction?

• A. Microalbuminuria
• B. Ketonuria
• C. Hematuria
• D. Urinary light chains

Answer: (A)

Microalbuminuria is the best early warning sign because it reflects a subtle loss of albumin through a gradually weakening glomerular filtration barrier. Albumin is a relatively small protein, and when the glomerular barrier begins to fail, it is the first to cross into the urine in small amounts. These small leaks precede the more obvious proteinuria that standard dipsticks detect, so testing for microalbumin provides sensitive detection of early glomerular dysfunction. This is especially important in people at high risk, like those with diabetes or high blood pressure, where early identification allows timely interventions (such as renin–angiotensin system blockade and strict metabolic/blood pressure control) to slow or prevent overt kidney disease.

Ketonuria indicates metabolic or diabetic states (like ketoacidosis or fasting), not glomerular permeability. Hematuria signals bleeding and can accompany various conditions, including nephritic processes, but it is not a reliable early marker of glomerular leakage. Urinary light chains point to plasma cell disorders or tubular handling issues and are not used as an early screen for glomerular dysfunction.