Medical Analysis
MCH (Mean Corpuscular Haemoglobin)
Mean Corpuscular Haemoglobin, commonly known as MCH, is one of the most important key red blood cell (RBC) indices used in medical diagnostics. It measures the average amount of haemoglobin contained within each red blood cell. The value of MCH is expressed in picograms (pg) per red blood cell.
How it is measured?
MCH can be determined using two primary methods:
Manual Method: In previous years, total haemoglobin and the red blood cell count were measured manually. In this method, haemoglobin is measured in Gms% and the RBC count is determined in millions/c.mm.
Calculation: The formula to calculate MCH (pg/per RBC) is:
MCH = (Hb in Gms%) / (RBCs count in millions/ul)
Electronic Cell Counter: Modern laboratories use automated electronic cell counters. These devices utilize the same mathematical formula as the manual calculation but perform the measurement through automation for higher efficiency and accuracy.
Judging MCH Manually on Peripheral Smear
Medical professionals can also assess MCH manually by observing a peripheral blood smear:
Central Pallor Observation: MCH is judged by observing the central pallor of the red blood cells. Under normal conditions, this pallor covers one-third of the cell’s diameter.
Hypochromia: If the central pallor is increased, it indicates low MCH levels, a condition known as hypochromia.
Hyperchromic Appearance: If the central pallor is decreased, it suggests a high MCH level, which may appear hyperchromic.
Microscopic Comparison: Technicians check the overall cell color and hemoglobin density by comparing the red blood cells to the nuclei of small lymphocytes.
Normal MCH: The size of a normal RBC is typically comparable to the size of a lymphocyte nucleus.
Physiological Significance
MCH provides essential insights into blood health:
It directly reflects the haemoglobin content of each individual red blood cell.
It offers vital information regarding the efficiency of oxygen transport throughout the body.
It serves as a key indicator of the oxygen-carrying capacity per red blood cell.
Along with Mean Corpuscular Volume (MCV) and Mean Corpuscular Haemoglobin Concentration (MCHC), it is crucial for the classification of various types of anemia.
It assists clinicians in diagnosing and differentiating other complex blood disorders.
MCH and its Use in Anemia Diagnosis
The relationship between MCV and MCH is foundational for diagnosing the nature of red blood cells and identifying clinical possibilities regarding anemia.
| MCV | Nature of RBCs | Clinical Possibilities |
| 27-32 | Normochromic | Anemia of chronic disease (e.g., chronic infections, inflammation, cancer), acute blood loss, chronic kidney disease, bone marrow failure (e.g., Aplastic anemia, myelofibrosis), endocrine disorders (e.g., Hypothyroidism, hypopituatrism), and Rheumatoid arthritis. |
| < 27 | Hypochromic | Iron Deficiency anemia, Thalassemia, Anemia of chronic disease (e.g., chronic kidney disease, Rheumatoid arthritis, Chronic infections), Sideroblastic anemia, and Lead poisoning. |
| 32 | Hyperchromic | Spherocytosis, Hereditary spherocytosis. |
Comparison of MCH & MCHC
While MCH and MCHC are related, they provide different diagnostic information.
| Feature | MCH | MCHC |
| Full Form | Mean Corpuscular Hb | Mean Corpuscular Hb Concentration |
| Definition | Average amount of Hb per RBC | Average concentration of Hb in packed RBCs |
| Unit | Picograms (pg) | g/dL or % |
| Formula | (Hb x 10) / RBC count | (Hb x 100) / Hct |
| Reflects | Hb content per cell | Hb concentration within cell |
| Normal Range | 27-32 pg | 30-35 g/dL |
| Low Value Indicates | Hypochromia (Iron deficiency) | Hypochromia (Iron deficiency) |
| High Value Indicates | Macrocytosis, B12/Folate deficiency | Spherocytosis or dehydration |
| Diagnostic Role | Helps classify anemia by Hb per cell | Helps assess RBC saturation with Hb |
Clinical Applications
MCH is a versatile tool in clinical practice:
It is an essential component in reaching a differential diagnosis for blood-related conditions.
It is used to monitor a patient’s response to treatment.
An increase in MCH is often suggestive of treatment effectiveness if the MCH was low at the time of initial diagnosis.
It is important to note that if the MCH was within the normal range at the time of the first diagnosis, clinicians must utilize other parameters and clinical judgment to assess treatment response rather than relying on MCH alone.
Reference Range of MCH
The normal reference ranges for MCH vary by age and category:
| Category | Normal Range |
| Newborn – Cord Blood | 33-47 pg/RBC |
| Newborn – Venous Blood | 30-40 pg/RBC |
| Adult Male/Female | 27-32 pg/RBC |
Abnormal Range of MCH
Abnormal values of MCH are categorized based on whether they fall on the lower or higher side of the reference ranges:
| Category | Lower Side (Pg/RBC) | Higher Side (Pg/RBC) |
| Newborn – Cord Blood | < 33 | More than 47 |
| Newborn – Venous Blood | < 30 | More than 30 |
| Adult Male/Female | < 27 | More than 32 |
Limitations and Considerations
It is important to remember that MCH is only one component of a Complete Blood Count (CBC). It does not carry significant diagnostic value unless it is considered alongside other blood indices and the patient’s overall clinical presentation.
For Non-Medicos
Understanding MCH: A Simple Guide to Your Red Blood Cells
When you receive a blood test result, you might see “MCH” on the report. MCH stands for Mean Corpuscular Haemoglobin. Simply put, it is a measurement of the average amount of haemoglobin—the protein in your red blood cells that carries oxygen—inside each one of your red blood cells.
Why is MCH Important?
Your body needs oxygen to function, and your red blood cells are the delivery vehicles for that oxygen. MCH helps your doctor understand:
How much oxygen your cells can carry.
Whether your red blood cells are healthy.
Whether you have anemia (a condition where your blood lacks enough healthy red blood cells).
How is it Measured?
In modern medical labs, MCH is calculated automatically by machines that count your blood cells and measure the total amount of haemoglobin in your blood sample.
What do the results mean?
Normal MCH: This usually means your red blood cells have a healthy amount of haemoglobin.
Low MCH (Hypochromic): If your MCH is too low, it often means your cells are “pale” because they don’t have enough haemoglobin. This is very commonly seen in iron deficiency anemia.
High MCH (Hyperchromic): A high MCH is less common and can sometimes be linked to issues like vitamin B12 or folate deficiencies.
Important Note for Patients
MCH is just one piece of a very large puzzle. Your doctor will never use MCH alone to diagnose a health condition. It must be looked at alongside other parts of your blood test, such as your red blood cell count and other indices, to give an accurate picture of your health. If your MCH levels are out of the normal range, do not panic; your doctor will interpret these results based on your unique health history and symptoms.
References:
Bain, B. J. (2015). Blood Cells: A Practical Guide. Wiley-Blackwell.
Hoffman, R., et al. (2017). Hematology: Basic Principles and Practice. Elsevier.
Kaushansky, K., et al. (2020). Williams Hematology. McGraw-Hill Education.
American Society of Hematology. (2023). “Clinical Practice Guidelines for Anemia.”
World Health Organization (WHO). (2011). “Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity.”
Kliegman, R. M., et al. (2022). Nelson Textbook of Pediatrics. Elsevier.
Lewis, S. M., et al. (2006). Dacie and Lewis Practical Haematology. Churchill Livingstone.
Rodgers, G. P., & Young, N. S. (2018). The Bethesda Handbook of Clinical Hematology. Lippincott Williams & Wilkins.
Greer, J. P., et al. (2014). Wintrobe’s Clinical Hematology. Wolters Kluwer.
Briggs, C., et al. (2007). “Quality assurance in haematology: a review of the role of the automated blood cell counter.” International Journal of Laboratory Hematology.
Means, R. T. (2022). “Approach to the Anemias.” Harrison’s Principles of Internal Medicine.
Ciesielski, C. A., et al. (2014). “Red blood cell indices: A review of the diagnostic utility in clinical practice.” Journal of Clinical Laboratory Analysis.
Savage, R. A. (2000). “Pseudodiagnosis of anemia: the role of the automated cell counter.” Laboratory Hematology.
Beutler, E. (2008). “The definition of anemia: what is the lower limit of normal of the blood hemoglobin concentration?” Blood.
Mehta, A. B., & Hoffbrand, A. V. (2014). Haematology at a Glance. Wiley-Blackwell.
FAQ’s:
Bain, B. J. (2015). Blood Cells: A Practical Guide. Wiley-Blackwell.
Hoffman, R., et al. (2017). Hematology: Basic Principles and Practice. Elsevier.
Kaushansky, K., et al. (2020). Williams Hematology. McGraw-Hill Education.
American Society of Hematology. (2023). “Clinical Practice Guidelines for Anemia.”
World Health Organization (WHO). (2011). “Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity.”
Kliegman, R. M., et al. (2022). Nelson Textbook of Pediatrics. Elsevier.
Lewis, S. M., et al. (2006). Dacie and Lewis Practical Haematology. Churchill Livingstone.
Rodgers, G. P., & Young, N. S. (2018). The Bethesda Handbook of Clinical Hematology. Lippincott Williams & Wilkins.
Greer, J. P., et al. (2014). Wintrobe’s Clinical Hematology. Wolters Kluwer.
Briggs, C., et al. (2007). “Quality assurance in haematology: a review of the role of the automated blood cell counter.” International Journal of Laboratory Hematology.
Means, R. T. (2022). “Approach to the Anemias.” Harrison’s Principles of Internal Medicine.
Ciesielski, C. A., et al. (2014). “Red blood cell indices: A review of the diagnostic utility in clinical practice.” Journal of Clinical Laboratory Analysis.
Savage, R. A. (2000). “Pseudodiagnosis of anemia: the role of the automated cell counter.” Laboratory Hematology.
Beutler, E. (2008). “The definition of anemia: what is the lower limit of normal of the blood hemoglobin concentration?” Blood.
Mehta, A. B., & Hoffbrand, A. V. (2014). Haematology at a Glance. Wiley-Blackwell.
