Diagnosis: Iron Deficiency Anemia (IDA)
In an adult patient with no significant medical history presenting with low hemoglobin and hematocrit, the most likely diagnosis is iron deficiency anemia, which must be confirmed with iron studies before proceeding with investigation for underlying causes. 1
Diagnostic Confirmation
Serum ferritin is the single most useful marker for confirming iron deficiency anemia, though transferrin saturation should be added if a false-normal ferritin is suspected (particularly in inflammatory states). 1
Key Laboratory Tests Required:
- Complete blood count with red cell indices to assess mean corpuscular volume (MCV) and red cell distribution width (RDW) 1, 2
- Serum ferritin (most sensitive single test for iron deficiency) 1
- Transferrin saturation (helpful when ferritin may be falsely elevated) 1
- Reticulocyte count to evaluate bone marrow response 2
Diagnostic Pitfall to Avoid:
Do not rely solely on hemoglobin and hematocrit measurements without iron studies, as normal CBC parameters can coexist with iron depletion, and many cases will be missed and misdiagnosed as normal. 3 Hemoglobin and hematocrit decrease only when severe iron depletion is already present and are often unreliable or misleading for early detection. 3
Confirming Iron Deficiency
A good response to iron therapy (hemoglobin rise ≥10 g/L within 2 weeks) is highly suggestive of absolute iron deficiency, even if iron study results are equivocal. 1
Investigating the Underlying Cause
Once iron deficiency anemia is confirmed, urgent investigation is mandatory because gastrointestinal malignancies can present with unexplained IDA, often without specific symptoms. 1
Initial Investigation Protocol:
- Detailed history focusing on: menstrual blood loss (in premenopausal women), gastrointestinal symptoms, dietary intake, medication use (NSAIDs, anticoagulants), and family history 1
- Urinalysis or urine microscopy to exclude urinary blood loss 1
- Celiac disease screening (serological testing or small bowel biopsy at gastroscopy), as celiac disease is found in 3-5% of IDA cases 1
Endoscopic Evaluation:
In men and postmenopausal women with newly diagnosed IDA, gastroscopy and colonoscopy should be the first-line gastrointestinal investigations. 1 In those not suitable for colonoscopy, CT colonography is a reasonable alternative. 1
Approximately one-third of men and postmenopausal women presenting with IDA have an underlying pathological abnormality, most commonly in the gastrointestinal tract. 1
Common Causes by Population
Premenopausal Women:
- Menstrual blood loss (menometrorrhagia can lead to severe IDA) 4
- Gastrointestinal pathology 1
- Poor dietary intake 5
Men and Postmenopausal Women:
- Gastrointestinal blood loss (including malignancy) 1
- Malabsorption (celiac disease, inflammatory bowel disease) 1
- Chronic kidney disease 6
All Adults:
- Chronic inflammatory diseases (anemia of chronic disease can coexist with or mimic IDA) 6
- Nutritional deficiency 5
- Medications (NSAIDs, anticoagulants) 1
Differential Diagnosis Considerations
While iron deficiency anemia is most likely, other causes of anemia must be excluded, particularly:
- Anemia of chronic disease (distinguished by increased ferritin, low iron, low transferrin) 6
- Vitamin B12 or folate deficiency (macrocytic anemia) 1, 6
- Hereditary hemoglobinopathies (thalassemia, sickle cell disease) 1
- Chronic kidney disease (normocytic anemia with elevated creatinine) 6
Critical Management Point
Do not initiate iron replacement therapy without confirming iron deficiency through iron studies and investigating for underlying causes, as this approach may mask serious pathology such as gastrointestinal malignancy. 1 The optimal management requires iron replacement therapy in combination with appropriate investigation to establish the underlying cause. 1