Which of the following is a common laboratory test used to evaluate iron deficiency anemia?

A common laboratory test used to evaluate iron deficiency anemia involves assessing both serum iron and ferritin levels. Serum iron measures the amount of circulating iron bound to transferrin, while ferritin is a protein that stores iron in the body. Low levels of both serum iron and ferritin are indicative of iron deficiency, as they reflect the depletion of iron stores and a reduced availability of iron for erythropoiesis, which can lead to anemia. This combination provides essential information about the body's iron status and assists in diagnosing and determining the severity of iron deficiency anemia.

Other tests provided in the question, such as potassium levels or the complete metabolic panel, do not specifically evaluate iron status or iron deficiency anemia. Similarly, B-type natriuretic peptide (BNP) is primarily used in the assessment of heart failure rather than in diagnosing or evaluating anemia. Thus, serum iron and ferritin remain the primary tests for assessing iron deficiency anemia.