What evaluations are indicated for a patient with hemoglobin 12 g/dL, hematocrit 38.8 %, mean corpuscular hemoglobin 25.8 pg, mean corpuscular hemoglobin concentration 30.9 g/dL, and mean platelet volume 12.6 fL?

Evaluation of Microcytic Hypochromic Anemia with Low MCH

This patient has microcytic hypochromic anemia (low MCH 25.8 pg, low MCHC 30.9 g/dL) and requires immediate iron studies including serum ferritin and transferrin saturation to confirm iron deficiency, followed by investigation of the underlying cause. 1, 2

Interpretation of Laboratory Values

Your patient's values indicate evolving iron deficiency:

• MCH of 25.8 pg is significantly low (normal 27-33 pg), indicating hypochromic red cells and serving as a more reliable marker of iron deficiency than MCHC because it is less dependent on storage conditions 1, 3
• MCHC of 30.9 g/dL is low (normal 32-36 g/dL), reflecting hypochromia from iron-restricted erythropoiesis 1
• Hemoglobin 12 g/dL represents borderline anemia in women (WHO cutoff <12 g/dL) or mild anemia depending on sex and race 1, 4
• The combination of low MCH with these values is highly suggestive of iron deficiency, even before frank microcytosis develops 1, 3

Required Diagnostic Workup

First-Line Iron Studies (Order Immediately)

• Serum ferritin is the single most powerful test to confirm iron deficiency, with <30 μg/L confirming iron deficiency without inflammation and <12-15 μg/L being diagnostic per WHO criteria 1, 2
• Transferrin saturation (TSAT) <15-20% supports iron deficiency and is less affected by inflammation than ferritin 1, 2, 3
• C-reactive protein (CRP) to assess for inflammation, which can falsely elevate ferritin and mask true iron deficiency 1, 3

Additional Essential Tests

• Absolute reticulocyte count to evaluate bone marrow response; a low or inappropriately normal count indicates impaired red cell production 5, 1, 3
• Complete blood count with differential to assess for abnormalities in other cell lines that might suggest bone marrow pathology 5

Interpretation Algorithm for Iron Studies

Once you obtain iron studies, interpret them as follows:

• If ferritin <30 μg/L without inflammation → confirms iron deficiency 1, 2
• If ferritin 30-100 μg/L with inflammation (elevated CRP) → still consistent with iron deficiency 1
• If ferritin >100 μg/L with TSAT <20% → suggests anemia of chronic disease 1
• If ferritin 30-100 μg/L → likely combination of iron deficiency and anemia of chronic disease 1

Investigation for Underlying Cause

Iron deficiency in adults always requires investigation for the source of blood loss:

For Premenopausal Women

• Detailed menstrual history including duration, frequency of pad/tampon changes, and passage of clots larger than a quarter, as heavy menstrual bleeding is the most common cause 1, 2
• Dietary iron intake assessment to identify inadequate intake 1
• History of blood donation 1

For Adult Men and Postmenopausal Women

• Gastrointestinal evaluation is mandatory to exclude malignancy, even without overt gastrointestinal symptoms or blood loss 1, 3
• Assess for gastrointestinal symptoms including dyspepsia, change in bowel habits, or abdominal pain 1

For All Patients

• Screen for malabsorption conditions including celiac disease, inflammatory bowel disease, or prior gastric surgery 3

Treatment Approach

• Oral iron supplementation (ferrous sulfate 325 mg containing 65 mg elemental iron, 1-3 times daily between meals) is first-line therapy once iron deficiency is confirmed 1, 2, 3
• 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 2
• Recheck CBC and iron studies after 1-3 months of therapy to confirm response 1, 2
• Intravenous iron may be considered if oral iron is not tolerated or absorbed, or when rapid repletion is needed 1

Critical Pitfalls to Avoid

• Do not assume normal hemoglobin excludes iron deficiency – the low MCH and MCHC indicate iron-deficient erythropoiesis is already occurring 1, 3
• If iron studies are normal, consider hemoglobinopathies such as thalassemia trait and obtain hemoglobin electrophoresis, particularly in patients of Mediterranean, African, or Southeast Asian descent 3
• Ferritin can be falsely elevated in the presence of inflammation, chronic disease, malignancy, or liver disease, which is why CRP measurement is essential 1, 3
• Combined iron and vitamin B12 deficiency can occur, particularly in elderly patients or those with inflammatory bowel disease, and may normalize the MCV while maintaining low MCH 3, 6

Note on Mean Platelet Volume (MPV)

• MPV of 12.6 fL is elevated (normal 7-11 fL), which can represent reactive thrombocytosis commonly accompanying iron deficiency anemia and typically resolves with iron repletion 2
• If thrombocytosis persists after iron correction, hematology referral is warranted to evaluate for primary myeloproliferative disorders 2