What are the next steps after abnormal Iron Deficiency Anemia (IDA) labs?

Management After Abnormal Iron Deficiency Anemia Labs

Once iron deficiency anemia is confirmed with iron studies (low ferritin being the single most useful marker), you should immediately initiate iron replacement therapy while simultaneously pursuing diagnostic investigations—do not delay treatment while awaiting workup unless colonoscopy is imminent. 1

Immediate Initial Steps

Confirm the Diagnosis

• Serum ferritin is the single most useful marker for confirming IDA, though transferrin saturation can help if false-normal ferritin is suspected (e.g., in inflammatory states) 1
• A good response to iron therapy (hemoglobin rise ≥10 g/L within 2 weeks) is highly suggestive of absolute iron deficiency, even with equivocal iron studies 1

Start Iron Replacement Immediately

• Begin oral iron therapy with one tablet daily of ferrous sulfate, fumarate, or gluconate 1
• If not tolerated, reduce to one tablet every other day, try alternative oral preparations, or consider parenteral iron 1
• Continue iron therapy for 3 months after anemia correction to replenish iron stores 1
• Monitor hemoglobin response within the first 4 weeks—expect a 1-2 g/dL increase within 4-8 weeks 1

Diagnostic Workup (Performed Concurrently with Treatment)

Essential Initial Investigations

All patients require:

• Urinalysis or urine microscopy to exclude urinary tract bleeding 1, 2
• Coeliac disease screening (tissue transglutaminase antibody with IgA level), as 3-5% of IDA cases have coeliac disease 1, 2
• Detailed history focusing on NSAID/aspirin use, dietary intake, family history of bleeding disorders or telangiectasia, and GI bleeding symptoms 1, 2

Endoscopic Evaluation

For men and postmenopausal women:

• Bidirectional endoscopy (gastroscopy AND colonoscopy) is first-line investigation 1, 2
• Gastroscopy reveals a cause in 30-50% of patients 1, 2
• Obtain small bowel biopsies during gastroscopy even if mucosa appears normal, as 2-3% have coeliac disease 1, 2
• Perform colonoscopy even if upper endoscopy finds a lesion, as dual pathology occurs in 10-15% of patients 1, 2
• Do not accept minor upper GI lesions (esophagitis, erosions, aphthous ulceration, peptic ulcer) as the sole cause without completing lower GI evaluation 1
• CT colonography is a reasonable alternative if colonoscopy is not suitable 1

For premenopausal women:

• Menstrual loss, pregnancy, and breastfeeding are common causes 1
• Bidirectional endoscopy is not routinely required in premenopausal women under 40 years without red flags 3
• However, if symptoms persist despite iron replacement or there are concerning features, proceed with full evaluation 2

Further Investigation for Negative Initial Workup

Proceed with additional testing if:

• Inadequate response to iron replacement therapy 1, 2
• Recurrent IDA after initial correction 1, 2
• Transfusion-dependent anemia 1

Small Bowel Evaluation

• Capsule endoscopy is the preferred test for examining the small bowel, as it is highly sensitive for mucosal lesions 1, 2
• CT/MRI enterography may be considered if capsule endoscopy is not suitable, and these are complementary for inflammatory and neoplastic disease 1, 2
• Small bowel radiology is rarely useful unless Crohn's disease is suspected 1

When to Stop Further Investigation

• After negative capsule endoscopy of acceptable quality, further GI investigation is only needed if ongoing IDA persists after iron replacement 1
• Long-term iron replacement may be appropriate when the cause of recurrent IDA is unknown or irreversible 1

Monitoring and Follow-Up

Laboratory Monitoring

• Recheck CBC and iron parameters (ferritin, TSAT) 4-8 weeks after the last infusion—do not check within 4 weeks as circulating iron interferes with assays 1
• Goal ferritin is 50 ng/mL in the absence of inflammation 1
• TSAT <20% has high sensitivity for diagnosing absolute or functional iron deficiency 1

Long-Term Follow-Up

• Monitor hemoglobin and red cell indices every 3 months for one year, then after another year 1
• Give additional oral iron if hemoglobin or MCV falls below normal 1
• Further investigation is only necessary if hemoglobin and MCV cannot be maintained with iron supplementation 1

Common Pitfalls to Avoid

• Do not defer iron replacement while awaiting investigations (unless colonoscopy is imminent) 1, 2
• Do not stop investigation after finding minor upper GI lesions—complete the full evaluation 1, 2
• Do not assume dietary deficiency as the sole cause without proper workup 2
• Do not rely on symptoms to guide investigation, as they rarely correlate with findings 2
• Do not perform faecal occult blood testing—it is insensitive and non-specific 1
• Do not routinely assess liver function, renal function, or clotting studies unless history suggests systemic disease 1

Special Considerations

Inadequate Response to Treatment

If hemoglobin does not rise appropriately:

• Evaluate for ongoing blood loss 1
• Consider alternative diagnoses 1
• Consider parenteral (intravenous) iron if oral intolerance, non-compliance, or malabsorption 1, 4, 3

Transfusion

• Limited transfusion of packed red cells may occasionally be required for symptomatic IDA, but iron replacement therapy is still necessary post-transfusion 1