Which statement best describes a Schilling test?

The Schilling test is specifically designed to assess vitamin B12 absorption and diagnose deficiencies related to this essential nutrient. In the test, radioactive cobalamin (vitamin B12) is administered orally, and the amount of this vitamin that is excreted in the urine is measured. If the body absorbs the cobalamin properly, a significant amount will appear in the urine. Conversely, if there is an issue with absorption—such as in pernicious anemia or other malabsorption syndromes—less cobalamin will be excreted. This objective measurement helps clinicians determine the underlying cause of vitamin B12 deficiency, differentiating between dietary deficiency and absorption problems.

The other choices pertain to different diagnostic tests for other conditions, but they do not describe the Schilling test. For instance, choices related to iron deficiency anemia, immune complexes in blood for hemolytic anemia, and folic acid measurements all focus on distinct nutrients or disorders, highlighting that the Schilling test is uniquely tied to evaluating vitamin B12 absorption.