Evaluation of Stable Microcytic Anemia with Thrombocytosis

Diagnostic Workup Required

The American College of Physicians recommends serum ferritin as the single most powerful test to confirm iron deficiency, with ferritin <30 μg/L confirming iron deficiency in the absence of inflammation, and <15 μg/L being diagnostic 1
Transferrin saturation (TSAT) <15-20% supports iron deficiency and is less affected by inflammation than ferritin 1
Reticulocyte count should be obtained to evaluate bone marrow response; a low or normal count indicates impaired red cell production 1

Reactive thrombocytosis commonly accompanies iron deficiency anemia and typically resolves with iron repletion 2
Platelet count >400 × 10³/μL has a positive likelihood ratio of 3.75 for giant cell arteritis in appropriate clinical contexts 2
Persistent thrombocytosis after iron correction would require hematology evaluation for primary myeloproliferative disorders 3

The American College of Physicians recommends obtaining iron studies immediately, including serum ferritin and transferrin saturation 1
If iron deficiency is confirmed, initiate ferrous sulfate 325 mg (65 mg elemental iron) 1-3 times daily between meals 1
Expect hemoglobin increase of 1-2 g/dL every 2-4 weeks, and continue iron for 3-6 months after hemoglobin normalizes to replenish stores 1
Recheck CBC after 3 months of iron therapy, and refer to hematology if iron studies are normal or thrombocytosis persists after iron correction 1

A detailed menstrual history is essential for premenopausal women, including duration of menses, frequency of pad/tampon changes, and passage of clots larger than a quarter 1
Heavy menstrual bleeding is the most common cause of iron deficiency in premenopausal women and may require gynecologic intervention if severe 1