Diagnostic Assessment: Iron Deficiency Anemia vs. Thalassemia Trait
This 15-year-old female most likely has concurrent iron deficiency anemia and beta-thalassemia trait, not one or the other. The laboratory findings show classic features of both conditions that must be addressed simultaneously.
Key Diagnostic Indicators
The lab results reveal a mixed picture requiring careful interpretation:
Features Suggesting Iron Deficiency:
- Low serum iron (45 μg/dL) confirms depleted iron stores 1
- Elevated RDW (16.6%) is highly sensitive (94%) for iron deficiency and distinguishes it from isolated thalassemia trait 2, 3
- Anisocytosis (1+) and hypochromasia (2+) reflect the heterogeneous red cell population typical of iron deficiency 2
- Elevated ESR (36 mm/hr) may indicate inflammation but does not exclude iron deficiency 4
Features Suggesting Thalassemia Trait:
- Markedly elevated RBC count (6.03 × 10¹²/L) with severe microcytosis (MCV 66.2 fL) is the hallmark pattern of thalassemia trait 1, 5
- Disproportionately low MCV relative to the degree of anemia strongly suggests thalassemia, as these patients characteristically produce increased numbers of small red cells 1
- The Mentzer index (MCV/RBC = 11) when <13 suggests thalassemia trait over pure iron deficiency 5
Critical Next Steps
Immediate Laboratory Workup Required:
You must obtain these tests to confirm the dual diagnosis:
- Ferritin level - A value <30 μg/L will definitively confirm iron deficiency in this adolescent 1
- Hemoglobin electrophoresis or HPLC - Elevated HbA2 >3.5% will confirm beta-thalassemia trait 1
- Complete iron panel including transferrin saturation (TSAT) - TSAT <20% confirms iron deficiency 1
- Reticulocyte count - Helps assess bone marrow response 6
The elevated RDW is particularly important here: while thalassemia trait alone typically has normal RDW, the elevated value (16.6%) indicates superimposed iron deficiency 2, 3, 7. Research shows that almost half of thalassemia cases can have elevated RDW when iron deficiency coexists 7.
Treatment Algorithm
Phase 1: Iron Repletion (Weeks 0-12)
Initiate therapeutic iron supplementation immediately:
- Prescribe 3-6 mg/kg/day of elemental iron (approximately 60 mg daily for this patient) 1
- Administer between meals to maximize absorption 6
- Provide dietary counseling emphasizing iron-rich foods, particularly heme iron sources 6
Phase 2: Reassessment (Week 8-12)
Recheck hemoglobin and iron parameters:
- Expect partial improvement only - Hemoglobin should increase by ≥1 g/dL if iron deficiency is present, but MCV will remain low if thalassemia trait is confirmed 1
- If hemoglobin increases appropriately, continue iron for 2-3 additional months to replete stores 6
- If no response after 4 weeks despite compliance, the diagnosis may be isolated thalassemia trait without true iron deficiency 6
Phase 3: Long-term Management
Once iron stores are repleted:
- Discontinue chronic iron supplementation - Thalassemia carriers do not benefit from ongoing iron and risk iron overload 1
- Document thalassemia diagnosis clearly in the medical record to prevent unnecessary future iron therapy 1
- Provide genetic counseling and recommend partner screening if family planning becomes relevant 1
- Screen annually for recurrent iron deficiency given her age and menstrual status 6
Common Pitfalls to Avoid
Do not assume this is isolated thalassemia trait based solely on the elevated RBC count. The low serum iron and elevated RDW indicate concurrent iron deficiency that requires treatment 2, 3.
Do not continue iron supplementation indefinitely. Once iron deficiency is corrected (confirmed by normalized ferritin), stop supplementation to avoid iron overload in a thalassemia carrier 1.
Do not rely on a single parameter. Ferritin can be falsely elevated by inflammation (note the elevated ESR), so use the complete iron panel including TSAT and response to therapy 6, 4.
Adolescent females are at particularly high risk for iron deficiency due to menstrual blood loss and often inadequate dietary intake 6. Screen annually for recurrence 6.