What is the significance of low Mean Corpuscular Hemoglobin (MCH) in a Complete Blood Count (CBC)?

From the Guidelines

Low MCH (Mean Corpuscular Hemoglobin) in a Complete Blood Count (CBC) is a reliable marker of iron deficiency, and patients with this condition should undergo further evaluation and treatment to address the underlying cause of iron deficiency. The significance of low MCH in a CBC is that it indicates hypochromia, a condition where red blood cells contain less hemoglobin than normal, which can lead to anemia 1. This condition is typically associated with iron deficiency, and the MCH is probably a more reliable marker of iron deficiency as it is less dependent on storage and the counting machine used 1.

Recommendation:

• If you have low MCH, consult your healthcare provider for a thorough evaluation and appropriate treatment.
• Specific steps typically include:
  1. Additional blood tests to confirm iron deficiency (serum ferritin, iron, and total iron-binding capacity) 1.
  2. Addressing the underlying cause (e.g., blood loss, poor iron absorption, or inadequate dietary intake).
  3. Iron supplementation, usually with ferrous sulfate 325 mg orally 1-3 times daily for 3-6 months.
  4. Dietary changes to increase iron intake (e.g., red meat, leafy greens, fortified cereals).
• In severe cases or if oral supplements are not tolerated, intravenous iron may be necessary.

Justification:

• MCH reflects the average amount of hemoglobin in each red blood cell 1.
• Low MCH often indicates that the body lacks sufficient iron to produce adequate hemoglobin, essential for oxygen transport.
• Treating the underlying cause and replenishing iron stores can improve MCH levels and overall health.
• It is essential to note that the specificity of MCH for iron deficiency is limited, as hypochromia also occurs in many hemoglobinopathies, sideroblastic anemia, and some cases of anemia of chronic disease 1.

Additional information:

• Monitor for side effects of iron supplements, such as constipation or stomach upset.
• Take iron supplements with vitamin C to enhance absorption, and avoid taking them with calcium-rich foods or antacids, which can interfere with iron absorption.
• Hb electrophoresis is recommended in those with microcytosis and normal iron studies, particularly if there is an appropriate ethnic background 1.

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 a multivariate analysis revealing that MCH level was an independent risk factor for APT discontinuation 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 chronic renal failure, where it may indicate a shortage of erythropoiesis factors, including iron, vitamin B12, and folates 5.
• Haemoglobinometry, which includes MCH measurement, can be a valuable primary screening test, but a full blood count is required when anaemia is present or when the patient's history and clinical signs indicate the need for such further investigation 6.