Mean Corpuscular Hemoglobin (MCH) is a measure of the average amount, or weight of Hemoglobin within a single Red Blood Cell. Mean Corpuscular Hemoglobin is calculated from the results of Hemoglobin test and Red Blood Cell count test. By knowing the Hemoglobin weight of a Red Blood Cell, it will be possible classify anemia, diagnose its type, and have a better idea of its causes. Depending on the cell’s hemoglobin amount, anemia can be classified into three classes:
- Normochromic Anemia: this class includes anemia types that occur without changes in Red Blood Cells color. Examples include anemia cased by Iron Deficiency or Renal Disease.
- Hypochromic Anemia: this class includes types of anemia associated with low MCH. In a Blood Smear test, Red Blood Cells will look pale under the microscope if the patient has Hypochromic Anemia. This class includes anemia caused by Lead Poisoning or Thalassemia.
Mean Corpuscular Hemoglobin is one of the Red Blood Cell Indices. To have a better classification of anemia, MCH is used with other RBC Indices (e.g. Mean Corpuscular Volume and Mean Corpuscular Hemoglobin Concentration). The calculation of Mean Corpuscular Hemoglobin is ordered routinely as a part of Complete Blood Cell Count.
MCH is derived by dividing the Hemoglobin Level (g/dL) by the total Red Blood Cell Count in a microliter and multiplying the result by 10. The final result will be the Red Blood Cell average hemoglobin weight measured in picograms (1/1012 grams). For example a patient who has a 16 g/dL Hemoglobin Level and 5 million RBCs/μL is going to have MCH equals to (15/5) x 10 pg or 30 pg (picograms).
Because Macrocytic cells (large cells) generally have more hemoglobin and microcytic cells have less hemoglobin, the causes for Mean Corpuscular Hemoglobin values closely resemble those for Mean Corpuscular Volume values. This has been documented with the use of automated counting instruments. The MCH adds very little information to the other indices. For this reason, Hemoglobin level needs to be compared with Hematocrit level in order to have a more accurate indication of hemoglobin concentration. This have led to the calculation of another member of the Red Blood Cell indices known as Mean Corpuscular Hemoglobin Centration (MCHC).
Causes of False Mean Corpuscular Hemoglobin Calculation
- Very high White Blood Cell count may cause automated cell counters to falsely calculate high Mean Corpuscular Hemoglobin.
- High lipid levels (>2000 mg/dL) causes automated cell counters to wrongfully indicate high hemoglobin levels which leads to wrong calculation of high MCH.
Normal Mean Corpuscular Hemoglobin
Infants are normally have a higher Mean Corpuscular Hemoglobin than adults. This is because Infants normally have larger Red Blood Cells than adults which causes more hemoglobin to be found per cell. The following are the Normal MCH levels for both newborns and adults:
Newborn: 32 to 36 pg.
Child or Adult: 27 to 31 pg.
Causes of High Mean Corpuscular Hemoglobin Levels
High MCH levels are associated with Macrocytic anemia which occur when Red Blood Cell size is abnormally large. Examples of Mcarocytic anemia causes include Vitamin B12 deficiency, Chemotherapy, and Myeloid Leukemia.
Causes of low Mean Corpuscular Hemoglobin
Low Mean Corpuscular Hemoglobin is associated with Microcytic Anemia which occurs when Red Blood Cells are abnormally small in Size. It should make sense that a smaller Red Blood Cell is going to have a fewer amount of Hemoglobin. Examples of Micorcytic Anemia include Thalassemia and Renal Disease Anemia.
Low MCH is also associated with Hypochomic Anemia which occurs when Red Blood Cells look pale under the microscope in a Blood Smear examination due to low hemoglobin found within a single RBC compared to its size. Examples of Hypochronic Anemia include late conditions of Iron Deficiency and Lead Poisoning.