For a client suspected of having pernicious anemia, which diagnostic test is most likely to be prescribed?

The Schilling test is specifically designed to assess vitamin B12 absorption, which is crucial in diagnosing pernicious anemia. In this condition, the body cannot adequately absorb vitamin B12 due to a lack of intrinsic factor, a protein essential for B12 absorption in the intestines. The Schilling test involves administering radioactive vitamin B12 and measuring its excretion in urine. Typically, if levels are low despite adequate intake, it suggests a malabsorption issue, confirming a diagnosis of pernicious anemia.

Other tests listed, such as the sweat test and haptoglobin test, focus on different conditions—like cystic fibrosis and hemolytic anemia, respectively—making them irrelevant in this context. Antinuclear antibodies are generally used to diagnose autoimmune disorders and do not specifically relate to vitamin B12 absorption or pernicious anemia. Thus, the Schilling test is the most appropriate diagnostic tool for identifying pernicious anemia due to its direct relationship with vitamin B12 metabolism.