A 68-year-old man presents to the clinic with progressive fatigue, tingling in both feet, and mild memory impairment over the past 6 months. He has a past medical history of primary hypothyroidism and vitiligo. Physical examination reveals a smooth, beefy-red tongue, pale conjunctivae, and diminished vibratory and position sensation in his bilateral lower extremities. Arrange the following diagnostic laboratory tests in the most appropriate sequential order to evaluate and establish the precise etiology of this patient's condition.
- 1Complete blood count (CBC) with peripheral blood smear
- 2Serum vitamin B12 and folate levels
- 3Serum methylmalonic acid (MMA) and homocysteine levels
- 4Anti-intrinsic factor antibodies
Cevap
The correct sequence is to first identify the anemia (CBC with smear), screen for the specific vitamin deficiency (serum B12 and folate), confirm functional tissue deficiency if needed (MMA and homocysteine), and finally determine the exact autoimmune etiology (anti-intrinsic factor antibodies).
The patient's clinical presentation (fatigue, sensory neuropathy, glossitis) combined with a history of other autoimmune disorders (vitiligo, hypothyroidism) strongly suggests pernicious anemia. The standard, evidence-based laboratory sequence progresses from broad to specific. It begins by characterizing the hematologic deficit (CBC with smear), followed by primary screening for the suspected nutritional deficit (B12 and folate). Because serum B12 can be falsely reassuring in up to 30% of deficient patients, functional metabolites (MMA and homocysteine) are ordered next to confirm tissue-level deficiency. Finally, finding the underlying root cause requires testing for anti-intrinsic factor antibodies to definitively diagnose pernicious anemia.
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Anahtar Kavram
Diagnostic sequencing for megaloblastic anemia and pernicious anemia