Mild Iron-Deficiency Anemia in an Adolescent Female
Direct Answer
This 17-year-old female has mild iron-deficiency anemia and requires a complete iron panel (serum ferritin, transferrin saturation, TIBC) plus C-reactive protein to confirm the diagnosis, followed by oral iron supplementation at 100 mg elemental iron daily. 1
Why This Is Iron-Deficiency Anemia
The hemoglobin of 11.8 g/dL meets WHO criteria for mild anemia in females ≥15 years (defined as Hb 11.0–11.9 g/dL), and the hematocrit of 35.2% is below the normal threshold of 36%. 1
Iron deficiency is the most common cause of anemia in adolescent females, with prevalence exceeding 50% in some cohorts due to menstrual blood loss, rapid growth, and inadequate dietary iron intake (typically below the recommended 15 mg/day). 1
The AST of 11 IU/L is normal and rules out liver disease as a cause of anemia; AST levels in alcoholic liver disease are typically elevated 2–6 times the upper limit of normal, and other hepatic causes would show elevated transaminases. 2
Required Diagnostic Workup
First-Line Iron Studies (All Must Be Ordered Together)
Serum ferritin <30 µg/L confirms iron deficiency when inflammation is absent and is the single most reliable marker for depleted iron stores. 1
Transferrin saturation <15–16% supports iron deficiency and is less affected by acute inflammation than ferritin, helping differentiate iron deficiency from anemia of chronic disease. 1
Total iron-binding capacity (TIBC) >45 µmol/L is another indicator of iron deficiency. 1
C-reactive protein (CRP) must be measured concurrently because ferritin rises as an acute-phase reactant during inflammation; a normal CRP is required to interpret low ferritin accurately and avoid missing true iron deficiency masked by inflammation. 1
Additional Helpful Tests
Reticulocyte count (corrected for anemia) is critical to confirm inadequate bone marrow response; a low or "inappropriately normal" reticulocyte index in an anemic patient indicates impaired marrow production consistent with iron deficiency. 1, 3
Red-cell indices (MCV, MCH, MCHC, RDW) help stage iron deficiency; low MCH (mean corpuscular hemoglobin) is the most sensitive early marker of iron-deficient erythropoiesis, even before microcytosis develops. 1
Common Pitfalls to Avoid
Do not rely on ferritin alone without CRP; inflammation can falsely elevate ferritin and mask true iron deficiency, leading to missed diagnoses. 1
Do not assume a normal MCV excludes iron deficiency; early iron deficiency may present with normocytic anemia before microcytosis develops. 1
Do not limit evaluation to a CBC alone; WHO criteria for anemia require full iron studies (ferritin, transferrin saturation, TIBC, CRP) for proper diagnosis. 1
A "normal" absolute reticulocyte count in an anemic patient is actually abnormal and represents an inadequate marrow response; correction for the degree of anemia is essential to avoid misinterpretation. 3
Staging of Iron Deficiency
Stage 1 (Iron depletion): Low ferritin only, no functional impairment. 1
Stage 2 (Iron-deficient erythropoiesis): Low ferritin plus low transferrin saturation, indicating impaired red-cell production. 1
Stage 3 (Iron-deficiency anemia): Adds low hemoglobin/hematocrit with microcytic, hypochromic red cells. 1
This patient is most likely in Stage 2 or early Stage 3, underscoring the need for the full iron panel to stage disease accurately. 1
Investigation for Underlying Cause
Assess menstrual blood loss as the leading cause in premenopausal women; heavy menstrual bleeding may necessitate gynecologic referral if menstrual losses seem inadequate to explain the deficiency. 1
Take a careful history of NSAID use and gastrointestinal symptoms (abdominal pain, diarrhea, melena) to assess for gastrointestinal blood loss. 1
Consider celiac disease screening with tissue transglutaminase (tTG) antibody testing, as malabsorption is a significant cause of iron deficiency with a prevalence of approximately 5% in iron-deficiency anemia. 1
Treatment Approach
Oral iron supplementation is first-line therapy for mild anemia (hemoglobin >10 g/dL), typically 100 mg elemental iron daily. 1
Recheck hemoglobin four weeks after initiating oral iron; an increase of ≥1 g/dL indicates true iron-deficiency anemia and an adequate therapeutic response. 1
If hemoglobin does not rise despite documented adherence, screen for celiac disease and evaluate for gastrointestinal blood loss to identify alternative or concurrent sources of iron loss. 1
Parenteral (intravenous) iron should be considered if oral iron is not tolerated due to gastrointestinal side effects or if there is malabsorption. 1
Blood transfusion is not indicated for mild anemia; it should be reserved for symptomatic anemia with cardiovascular instability such as fatigue, hypotension, or tachycardia. 1
Monitoring and Follow-Up
Recheck hemoglobin and iron studies after 1–3 months of iron supplementation to assess response. 1
Continue iron supplementation for 3–6 months after hemoglobin normalizes to replenish body iron stores. 1
Monitor for recurrence, as anemia recurs in more than 50% of patients within one year, often indicating ongoing blood loss or inadequate iron stores. 1
Alternative Causes If Iron Studies Are Normal
If iron studies are normal despite anemia, consider vitamin B12 or folate deficiency, hemoglobinopathies (especially in African, Mediterranean, or Southeast Asian ancestry), or chronic disease; appropriate additional testing (B12, folate levels, hemoglobin electrophoresis) should be ordered. 1, 4
Perform hemoglobin electrophoresis when microcytosis is present and the individual belongs to an at-risk ethnic group to rule out thalassemia or other hemoglobinopathies. 1