Elevated RBC and Platelets with Low MCV, MCH, and MCHC
This pattern most commonly indicates iron deficiency anemia, and you should immediately order a complete iron panel (serum ferritin, transferrin saturation, and C-reactive protein) to confirm the diagnosis and identify the underlying cause of iron loss. 1
Understanding the Laboratory Pattern
Low MCH and MCHC indicate hypochromic anemia—red blood cells contain less hemoglobin than normal—which strongly suggests iron deficiency. 1 MCH is actually a more reliable marker of iron deficiency than MCV because it reflects both absolute and functional iron deficiency and is less dependent on storage conditions and laboratory equipment. 1
The elevated RBC count occurs because the bone marrow attempts to compensate for reduced oxygen-carrying capacity by producing more red blood cells, even though each cell is smaller and contains less hemoglobin. 2 The elevated platelet count (thrombocytosis) frequently accompanies iron deficiency anemia and represents a reactive process. 2
Immediate Diagnostic Workup
Order the following tests to confirm iron deficiency: 1
- Serum ferritin: The single most specific test for iron deficiency. Ferritin <15 μg/L confirms absent iron stores, while <30 μg/L indicates low body iron stores. 1
- Transferrin saturation: Values <16-20% support iron deficiency and are less affected by inflammation than ferritin. 1
- C-reactive protein (CRP): Essential to assess for inflammation, which can falsely elevate ferritin levels. 1
- Reticulocyte count: Assesses bone marrow response; low or normal values indicate impaired red cell production. 1
Interpreting Ferritin in Context
Critical pitfall to avoid: Do not dismiss apparently normal ferritin values if inflammation is present, as ferritin is an acute-phase reactant and can mask true iron deficiency. 1
- Without inflammation: Ferritin <30 μg/L confirms iron deficiency. 1
- With inflammation: Ferritin up to 100 μg/L may still indicate iron deficiency; use higher cutoffs (45-100 μg/L) depending on inflammation severity. 1
- Ferritin >150 μg/L: Makes absolute iron deficiency unlikely even with inflammation. 1
- Ferritin 30-100 μg/L with inflammation: Consider combined true iron deficiency and anemia of chronic disease. 1
Alternative Diagnoses When Iron Studies Are Normal
If iron studies are normal despite low MCH/MCHC, obtain hemoglobin electrophoresis—especially in individuals of Mediterranean, African, or Southeast Asian descent—to evaluate for thalassemia trait. 1, 3 Thalassemia trait produces microcytosis with low MCH but normal iron parameters, and the MCV is typically reduced disproportionately to the degree of anemia. 1
In thalassemia with concurrent iron deficiency, hemoglobin, MCV, MCHC, and MCH values are significantly lower compared to isolated thalassemia. 3 Additional conditions to consider include anemia of chronic disease and sideroblastic anemia. 1
Treatment Approach for Confirmed Iron Deficiency
Initiate oral iron supplementation with ferrous sulfate 325 mg (65 mg elemental iron) 1-3 times daily between meals. 1 Expect hemoglobin increase of approximately 1-2 g/dL every 2-4 weeks. 1
Continue iron supplementation for 3-6 months after hemoglobin normalizes to replenish iron stores. 1 Check hemoglobin, reticulocytes, and iron studies after 4-8 weeks of therapy. 1
Consider parenteral iron if: 1
- Patient is intolerant to oral iron
- Poor response to oral iron
- Severe anemia requiring rapid correction
Investigating the Underlying Cause
Do not forget to investigate the cause of iron deficiency, as it often indicates ongoing blood loss requiring evaluation. 1 Common sources include gastrointestinal bleeding, menstrual blood loss, malabsorption (celiac disease, inflammatory bowel disease), or dietary insufficiency. 1
Diagnostic Confirmation via Therapeutic Response
A rise in hemoglobin of ≥10 g/L (≈1 g/dL) within 2 weeks of iron therapy strongly suggests absolute iron deficiency, even if iron study results are equivocal. 1 This therapeutic trial can be diagnostically useful when laboratory results are borderline or confounded by inflammation.