In a 17‑year‑old female with mild microcytic‑normochromic anemia (hemoglobin ≈11 g/dL, hematocrit ≈35 %, normal mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration, slightly elevated red cell distribution width) and normal platelets, aspartate aminotransferase and thyroid function, what laboratory tests and medications should be ordered?

Laboratory Evaluation and Treatment for Mild Microcytic Anemia in an Adolescent Female

Order serum ferritin and transferrin saturation immediately, and initiate oral ferrous sulfate 200 mg three times daily while awaiting results. 1

Diagnostic Laboratory Tests to Order

First-Line Iron Studies (Order Immediately)

• Serum ferritin is the single most powerful test for confirming iron deficiency, with levels <15 μg/L providing 99% specificity for absent iron stores and <30 μg/L indicating depleted body iron. 1
• Transferrin saturation (TSAT) should be measured alongside ferritin because it is more sensitive than hemoglobin alone for detecting iron deficiency, with values <16–20% confirming the diagnosis. 1
• C-reactive protein (CRP) must be obtained concurrently because ferritin is an acute-phase reactant that can be falsely elevated by inflammation, infection, or other conditions. 1

Interpretation Algorithm Based on Your Patient's Indices

Your patient has:

• RDW 14.3% (slightly elevated, >14.0%) combined with low MCV (implied by MCH 26.9)—this pattern strongly suggests iron deficiency anemia rather than thalassemia trait, which typically shows RDW ≤14.0%. 1
• Normal platelet count (334) argues against chronic bleeding or bone marrow pathology. 1

When to Order Hemoglobin Electrophoresis

• Do NOT order hemoglobin electrophoresis as a first-line test—reserve it only if iron studies return normal (ferritin >30 μg/L and TSAT >20%) or if the patient belongs to a high-risk ethnic group (African, Mediterranean, Southeast Asian ancestry). 1
• Hemoglobin electrophoresis is also indicated if anemia fails to improve after 4 weeks of adequate oral iron therapy despite documented compliance. 1

Medication to Prescribe Now

Oral Iron Supplementation (First-Line Treatment)

• Ferrous sulfate 200 mg three times daily is the recommended first-line treatment for microcytic hypochromic anemia, to be continued for at least three months after correction of anemia to replenish iron stores. 1
• Alternative formulations include ferrous gluconate or ferrous fumarate if ferrous sulfate causes intolerable gastrointestinal side effects. 1
• Adding ascorbic acid (vitamin C) can enhance iron absorption. 1

Expected Response and Monitoring

• Hemoglobin should rise ≥10 g/L (≥1 g/dL) within 2 weeks if iron deficiency is the cause—this therapeutic response confirms the diagnosis even when iron studies are equivocal. 1
• Monitor hemoglobin and red cell indices at three-monthly intervals for one year, then again after a further year. 1
• If hemoglobin or MCV falls below normal during follow-up, provide additional oral iron. 1

Investigation of Underlying Cause (Mandatory in Adolescents)

Assess for Sources of Iron Loss

• Heavy menstrual bleeding is the most common cause of iron deficiency in adolescent females and must be evaluated through menstrual history (duration, frequency, pad/tampon use). 1
• Dietary assessment is crucial—adolescents following vegetarian or vegan diets are at increased risk for iron deficiency and should be screened for inadequate dietary iron intake. 1
• Gastrointestinal blood loss should be considered if menstrual history does not fully explain the anemia; perform stool guaiac testing for occult blood. 1

Critical Pitfalls to Avoid

• Do not assume all microcytic anemia is iron deficiency—anemia of chronic disease, thalassemia, and sideroblastic anemia require different management, but your patient's RDW >14% makes iron deficiency most likely. 1
• Do not delay treatment while awaiting iron studies—begin oral iron immediately in a 17-year-old with mild microcytic anemia, as the therapeutic response itself confirms the diagnosis. 1
• Do not overlook combined deficiencies—iron deficiency can coexist with vitamin B12 or folate deficiency, recognizable by elevated RDW, though this is less common in adolescents. 1
• Do not order bone marrow examination—it is unnecessary in straightforward microcytic anemia with typical indices and should be reserved for refractory cases or when genetic disorders are suspected. 1

When to Consider Rare Genetic Causes

• Genetic disorders of iron metabolism (IRIDA, SLC11A2 defects) should be considered only if the patient fails to respond to both oral and intravenous iron, has a family history of refractory anemia, or shows remarkably low TSAT with low-to-normal ferritin. 1
• X-linked sideroblastic anemia (ALAS2 defects) may warrant a trial of pyridoxine (vitamin B6) 50–200 mg daily if iron studies are normal but microcytosis persists, though this is exceedingly rare in adolescent females. 1