Question

a patient has a serum potassium level of 3 meq/l and a normal blood pressure. which test should be performed initially to assist with the differential diagnosis? plasma aldosterone plasma renin activity serum bicarbonate serum magnesium

Explanation:

When a patient has hypokalemia (serum potassium level of 3 mEq/L is below the normal range of 3.5 - 5.0 mEq/L) and normal blood pressure, checking serum bicarbonate helps in differentiating the cause. Metabolic alkalosis (which can be associated with certain causes of hypokalemia like vomiting - related losses) can be identified by elevated serum bicarbonate. Plasma aldosterone and plasma renin activity are more relevant when there are blood - pressure abnormalities (e.g., in hyperaldosteronism which often causes hypertension along with hypokalemia). Serum magnesium is important as hypomagnesemia can cause refractory hypokalemia, but initial assessment for acid - base status (via serum bicarbonate) is a key first step in the differential diagnosis of hypokalemia with normal blood pressure.

Answer:

Serum bicarbonate