From the Guidelines
This CBC shows a microcytic, hypochromic anemia pattern, most consistent with iron deficiency anemia, and further evaluation should include iron studies and potentially hemoglobin electrophoresis. The hemoglobin is slightly low at 12.6 g/dL (normal 13.0-17.7), while the hematocrit remains within normal range. The red cell indices reveal microcytosis (low MCV at 78 fL), hypochromia (low MCH at 23.6 pg and low MCHC at 30.1 g/dL), and anisocytosis (elevated RDW at 15.5%) 1. According to the British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults, MCH is probably a more reliable marker of iron deficiency as it is less dependent on storage and the counting machine used, and a reduction is seen in both absolute and functional iron deficiency (FID) 1. Some key points to consider in the evaluation of this patient include:
- Iron deficiency typically shows progressive changes in red cell indices before hemoglobin drops significantly 1
- The elevated RDW indicates variable red cell sizes, which is more characteristic of iron deficiency than thalassemia 1
- Serum ferritin (SF) is the most specific test for iron deficiency in the absence of inflammation, with an SF level of <15 μg/L indicative of absent iron stores, and SF levels of less than 30 μg/L generally indicative of low body iron stores 1
- An SF cut-off of 45 μg/L has been suggested as providing the optimal trade-off between sensitivity and specificity for iron deficiency in practice 1 Further evaluation should include iron studies (serum iron, ferritin, TIBC), and potentially hemoglobin electrophoresis if thalassemia is suspected. If iron deficiency is confirmed, oral iron supplementation (ferrous sulfate 325 mg daily or twice daily) would be recommended, along with investigation of the underlying cause of iron deficiency, such as occult bleeding or malabsorption.
From the Research
Interpretation of CBC Results
The provided CBC results indicate:
- Low hemoglobin (Hb) level at 12.6 g/dL, which is below the normal range of 13.0-17.7 g/dL 2, 3, 4
- Low hematocrit (Hct) level at 41.8%, which is below the normal range of 37.5-51.0% but still within the normal range for some populations 3, 5
- Low mean corpuscular volume (MCV) at 78 fL, which is below the normal range of 79-97 fL, indicating microcytic anemia 3, 4, 5
- Low mean corpuscular hemoglobin (MCH) at 23.6 pg, which is below the normal range of 26.6-33.0 pg 3, 5
- Low mean corpuscular hemoglobin concentration (MCHC) at 30.1 g/dL, which is below the normal range of 31.5-35.7 g/dL 3, 5
- High red blood cell distribution width (RDW) at 15.5%, which is above the normal range of 11.6-15.4% 5
Possible Causes of Microcytic Anemia
The causes of microcytic anemia can be acquired or congenital and include:
- Iron deficiency anemia, which is the most common cause of microcytic anemia 2, 3, 4, 5
- Thalassemia, which is a genetic disorder that affects the production of hemoglobin 3, 4, 5
- Anemia of chronic disease, which can be caused by chronic inflammation or infection 2, 3
- Sideroblastic anemia, which is a rare genetic disorder that affects the production of hemoglobin 3, 4
- Lead toxicity, which can cause microcytic anemia due to the inhibition of hemoglobin synthesis 2
Diagnostic Approach
To determine the cause of microcytic anemia, the following steps can be taken:
- Measure serum ferritin levels to determine if iron deficiency is present 2, 3, 4, 5
- Measure serum iron and transferrin saturation to determine if iron deficiency is present 2, 3
- Perform a peripheral blood smear to look for signs of hemoglobinopathy or other abnormalities 2, 3
- Consider genetic testing for thalassemia or other genetic disorders if suspected 4, 5