Diagnosis and Management of Iron Deficiency Anemia

Diagnostic Criteria

The combination of low MCH, low MCHC, and high RDW is highly suggestive of iron deficiency anemia, and serum ferritin should be checked to confirm the diagnosis, with a ferritin level <30 μg/L confirming iron deficiency in the absence of inflammation, according to the Journal of Crohn's and Colitis 1
High RDW with low MCH/MCHC indicates iron deficiency rather than thalassemia, with an elevated RDW (>14%) reflecting anisocytosis, which is characteristic of iron deficiency, as reported in the Journal of Crohn's and Colitis and Gut 1, 3
Ferritin <12 μg/L is diagnostic of iron deficiency regardless of inflammatory status, as stated in Gut 3, 5

Confirm iron deficiency with serum ferritin, and in the presence of inflammation, ferritin up to 100 μg/L may still indicate iron deficiency, according to the Journal of Crohn's and Colitis 1
Transferrin saturation <30% supports the diagnosis, as reported in Gut 5, 6
Check reticulocyte count to assess bone marrow response, and measure CRP to determine if inflammation is present, as recommended in the Journal of Crohn's and Colitis 1

For adult men and post-menopausal women, gastrointestinal evaluation is mandatory, including upper GI endoscopy with small bowel biopsies and lower GI endoscopy, to exclude coeliac disease and colorectal cancer, as stated in Gut 3, 6
Common GI causes include NSAID use, colorectal cancer/polyps, gastric cancer, angiodysplasia, and coeliac disease, as reported in Gut 3, 5
Document medication history, including NSAIDs and aspirin, which should be stopped whenever possible, and anticoagulant use, which should not deter investigation, as recommended in Gut 5, 6

Initiate oral or intravenous iron supplementation once diagnosis is confirmed, as recommended in Praxis Medical Insights, but prioritizing Gut 5, 3
Response to three weeks of oral iron can confirm true iron deficiency if diagnostic uncertainty remains, as stated in Gut 3, 5

Do not assume thalassemia based on ethnicity alone, as high RDW strongly argues against thalassemia trait and favors iron deficiency, as reported in Gut 3
Do not skip GI investigation in adult men and post-menopausal women, as occult malignancy must be excluded, as stated in Gut and prioritizing Gut over Praxis Medical Insights 5, 6
Do not overlook combined deficiencies, as iron deficiency can coexist with folate or B12 deficiency, which may normalize MCV but maintain elevated RDW, as reported in Gut 3
Do not attribute IDA to dietary causes without investigation, as GI blood loss is the most common cause in adult men and post-menopausal women, as stated in Gut 5