From the Guidelines
Low MCH (Mean Corpuscular Hemoglobin) in a Complete Blood Count (CBC) is a significant indicator of iron deficiency anemia, and prompt treatment is essential to prevent complications associated with chronic anemia. The most recent and highest quality study, published in 2021 in the journal Gut, suggests that MCH is a reliable marker of iron deficiency, and a reduction in MCH is seen in both absolute and functional iron deficiency 1.
Causes and Treatment
The causes of low MCH include:
- Iron deficiency anemia
- Thalassemia
- Chronic disease
- Sideroblastic anemia
- Vitamin B12 or folate deficiency Treatment usually involves iron supplementation, and the study recommends investigating and addressing the cause of iron deficiency 1.
Investigation and Management
Key points to consider in the investigation and management of low MCH include:
- 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 1
- An SF cut-off of 45 μg/L provides a respectable specificity of 0.92 for iron deficiency 1
- Hemoglobin electrophoresis is recommended in those with microcytosis and normal iron studies, particularly if there is an appropriate ethnic background 1
- Follow-up CBCs should be performed every 2-4 weeks to monitor response to treatment
Importance of Prompt Treatment
Understanding MCH is crucial because it reflects the oxygen-carrying capacity of red blood cells. Addressing low MCH promptly can prevent complications associated with chronic anemia, such as fatigue, weakness, and cardiovascular strain. Prompt treatment of iron deficiency anemia is essential to improve morbidity, mortality, and quality of life.
From the Research
Significance of Low Mean Corpuscular Hemoglobin (MCH) in a Complete Blood Count (CBC)
- Low MCH levels can be an indicator of iron deficiency or hemoglobinopathy, as seen in a study of apheresis donors where 64% of those with low MCV values had iron deficiency 2.
- A low MCH level is also a predictor of discontinuation of antiplatelet therapy in patients with acute coronary syndrome, with patients having low MCH (<30.0 pg) being more likely to discontinue therapy 3.
- In patients with microcytic anemia, a low MCH level can be used in conjunction with other parameters, such as platelet count, to differentiate between pure iron deficiency anemia and combined deficiencies of vitamin B12 and iron 4.
- Low MCH levels can also be associated with other conditions, such as folate and B12 deficiencies, although increased RDW values may be a more sensitive indicator of these deficiencies 5.
- Haematological setpoints, including MCH, are stable and patient-specific, and can be used to personalize the interpretation of CBC results and improve the detection of certain conditions, such as iron deficiency 6.