From the Guidelines
When hemoglobin levels are normal but MCV is low and MCHC is high, the most likely diagnosis is thalassemia trait, particularly beta thalassemia minor, due to its characteristic presentation of microcytosis and elevated MCHC despite normal hemoglobin levels. This pattern suggests microcytic hypochromic anemia with compensatory mechanisms maintaining normal hemoglobin. The possibilities include thalassemia trait, hemoglobinopathies, or iron deficiency anemia in early stages with ongoing treatment. According to the British Society of Gastroenterology guidelines 1, microcytosis and hypochromia are common in iron deficiency, but thalassemia trait is a more likely cause when MCV is reduced out of proportion to the level of anemia.
Further testing is recommended, including:
- Hemoglobin electrophoresis to identify abnormal hemoglobin variants 1
- Serum iron studies to rule out iron deficiency 1
- Potentially genetic testing if thalassemia is suspected
These conditions generally require no treatment if hemoglobin remains normal, but genetic counseling may be appropriate for thalassemia carriers, especially for family planning purposes, as two carriers can have children with more severe forms of thalassemia. It is essential to distinguish between iron deficiency anemia and anemia of chronic disease, as the management of these conditions differs, particularly in patients with inflammatory bowel diseases 1.
Key points to consider:
- Microcytosis and hypochromia are not exclusive to iron deficiency and can occur in thalassemia trait and other hemoglobinopathies
- Serum ferritin levels can be elevated in the presence of inflammation, making it challenging to diagnose iron deficiency 1
- A comprehensive workup, including complete blood count, reticulocytes, serum ferritin, transferrin saturation, and CRP, is necessary to determine the underlying cause of anemia 1
From the Research
Implications of Normal Hemoglobin Levels with Low MCV and High MCHC
- Normal Hemoglobin (Hb) levels with low Mean Corpuscular Volume (MCV) and high Mean Corpuscular Hemoglobin Concentration (MCHC) may indicate iron deficiency or other underlying conditions 2, 3, 4.
- Low MCV values can be found in patients with iron deficiency, even if Hb levels are normal 2, 3.
- High MCHC values can be seen in cases of hereditary spherocytosis, where patients may have relative iron deficiency 5.
- The diagnostic accuracy of MCV, MCH, and MCHC in diagnosing empty iron stores is moderate, and normal values do not exclude empty iron stores in anemic patients 3.
- False elevation of MCHC can occur due to interference such as cold agglutination and lipid blood, and correcting for these interferences is essential for accurate diagnosis 6.
Possible Underlying Conditions
- Iron deficiency: Low MCV and high MCHC can be indicative of iron deficiency, even if Hb levels are normal 2, 3, 4.
- Hereditary spherocytosis: High MCHC values can be seen in cases of hereditary spherocytosis, where patients may have relative iron deficiency 5.
- Other conditions: Normal Hb levels with low MCV and high MCHC can also be seen in other conditions, such as anemia of chronic disease or thalassemia, and further testing may be necessary to determine the underlying cause 2, 3, 4.