Iron Deficiency Anemia
Your laboratory findings—low MCH, low MCHC, high RDW-CV, low serum iron, low transferrin saturation, and low ferritin—establish the diagnosis of iron deficiency anemia, and you should initiate oral iron supplementation immediately while investigating the underlying cause of blood loss. 1, 2
Diagnostic Confirmation
Your constellation of laboratory values is pathognomonic for iron deficiency anemia:
- Low ferritin confirms depleted iron stores, as ferritin <30 µg/L is the diagnostic criterion for iron deficiency in patients without inflammation 2
- Low transferrin saturation (<20%) confirms inadequate iron availability for erythropoiesis and is the primary cutoff to establish iron deficiency 2
- High RDW-CV (>14%) indicates increased variation in red blood cell size, which is characteristic of iron deficiency anemia and helps differentiate it from thalassemia minor 1, 3
- Low MCH and MCHC reflect the microcytic, hypochromic nature of red blood cells produced under iron-deficient conditions 4, 5
The combination of low MCV (implied by low MCH), high RDW, and transferrin saturation <16% together with microcytic-hypochromic red cells strongly supports iron deficiency anemia 2. MCH has the highest correlation with hemoglobin in iron deficiency and can identify 97-100% of anemic, iron-deficient individuals 4.
Treatment Protocol
Oral Iron Therapy
- Start ferrous sulfate 200 mg three times daily (providing approximately 195 mg of elemental iron per day) 2
- Continue treatment for at least 3 months after hemoglobin correction to replenish iron stores 2, 6
- Check hemoglobin at one month; you should see a 1-2 g/dL increase if treatment is effective 5
If Oral Iron Fails
If hemoglobin does not increase by 1-2 g/dL after one month, consider three possibilities 5:
- Malabsorption of oral iron (celiac disease, atrophic gastritis, H. pylori infection) 2
- Continued bleeding that exceeds the rate of iron replacement
- Undiagnosed lesion causing ongoing blood loss
In cases of oral iron refractoriness, exclude autoimmune atrophic gastritis, Helicobacter pylori infection, and celiac disease before pursuing genetic testing for iron-refractory iron deficiency anemia (IRIDA) 2. IRIDA, caused by TMPRSS6 mutations, presents with very low transferrin saturation, low-to-normal ferritin, and lack of response to oral iron 2, 7.
Mandatory Investigation for Blood Loss
In adult men and postmenopausal women, gastrointestinal blood loss from occult malignancy is the most frequent cause of iron deficiency and must be investigated 2. Nine percent of patients older than 65 years with iron deficiency anemia have a gastrointestinal cancer when evaluated 5.
- Begin with colonoscopy if the patient is older than 50 years 5
- Perform upper endoscopy if colonoscopy is negative or if upper GI symptoms are present
- In premenopausal women, menstrual blood loss is the most common cause, but GI evaluation is still warranted if dietary history and review of symptoms suggest other sources 5
Common Pitfalls to Avoid
- Do not assume mild anemia is clinically insignificant; no evidence supports down-ranking its importance, and it may indicate serious underlying disease 2
- Do not stop iron therapy when hemoglobin normalizes; you must continue for 3 months afterward to replenish stores 2, 6
- Do not rely on serum ferritin alone in patients with inflammation (elevated CRP/ESR), as ferritin is an acute-phase reactant and may be falsely elevated despite true iron deficiency 1, 2
- Avoid "milking" the finger during capillary blood sampling, as excessive squeezing contaminates blood with tissue fluid and produces falsely low readings 1
Monitoring Response
- Recheck complete blood count at one month to confirm a 1-2 g/dL hemoglobin increase 5
- Measure serum ferritin after completing the 3-month replenishment phase to document restored iron stores 6
- If no response occurs, reassess for malabsorption, ongoing blood loss, or consider parenteral iron therapy 2, 8