The Mean Corpuscular Hemoglobin Concentration (MCHC) test is a measurement included as part of a Complete Blood Count (CBC). It quantifies the average concentration of hemoglobin found within a given volume of red blood cells. Hemoglobin is the protein responsible for transporting oxygen from the lungs to the body’s tissues, making MCHC an important indicator of the blood’s oxygen-carrying capacity. Analyzing the MCHC helps medical professionals gain insight into potential conditions affecting red blood cell production and function.
The Role and Calculation of MCHC
The MCHC is one of several red blood cell indices used to describe the physical characteristics of red blood cells. This specific index measures the saturation of hemoglobin relative to the size of the red blood cell. Unlike other indices that measure the average amount of hemoglobin per cell, MCHC focuses on the density of the hemoglobin within the cell volume.
The MCHC value is not measured directly but is mathematically derived from two other results obtained in the CBC panel. The calculation requires the total hemoglobin concentration and the hematocrit, which is the percentage of blood volume occupied by red blood cells. The formula used is to divide the hemoglobin value by the hematocrit value. The result is typically expressed in grams per deciliter (g/dL) or grams per liter (g/L), providing a standardized way to assess how densely packed the oxygen-carrying protein is inside the cell.
Standard Procedure and Preparation
The MCHC test is conducted using a small blood sample collected through a routine procedure called venipuncture. A healthcare provider inserts a needle, usually into a vein in the arm, to draw the blood into a collection tube. The procedure is quick, typically lasting only a few minutes, and involves minimal discomfort.
Because the MCHC is part of a standard CBC, no special preparation is generally required before the test. Patients can usually eat and drink normally beforehand. If other blood panels like a lipid profile or glucose test are ordered simultaneously, fasting may be necessary, and the provider will give specific instructions. The blood sample is sent to a laboratory for automated analysis, and results are typically available within a few days.
Interpreting Normal Ranges
A result that falls within the established reference range indicates that the red blood cells are carrying an appropriate concentration of hemoglobin. The standard normal range for MCHC is generally considered to be between 32 and 36 grams per deciliter (g/dL). A value in this range suggests the red blood cells are properly saturated and performing their oxygen transport function normally.
The normal range can vary slightly based on the specific laboratory and the automated analyzer equipment used. Results should always be compared to the reference range printed on the laboratory report. A result within the normal limits confirms that the red blood cells appear neither too pale nor too densely colored, a condition known as normochromia.
Understanding Abnormal MCHC Levels
Low MCHC (Hypochromia)
A low MCHC result, known as hypochromia, signifies that the red blood cells contain a lower-than-normal concentration of hemoglobin. This condition is most frequently linked to iron deficiency anemia, the most common type of anemia worldwide. When the body lacks sufficient iron, the body cannot produce enough hemoglobin to fill the red blood cells adequately.
Other conditions that lead to low MCHC include hereditary disorders such as thalassemia, which impairs the production of functional hemoglobin. Chronic blood loss from sources like heavy menstrual periods or gastrointestinal issues can also deplete iron stores over time. In these cases, the low MCHC often correlates with a low Mean Corpuscular Volume (MCV), meaning the red blood cells are also smaller than usual.
High MCHC (Hyperchromia)
A high MCHC result, or hyperchromia, is less common and suggests that the red blood cells have an abnormally high concentration of hemoglobin. This concentration occurs because the hemoglobin is packed into a smaller volume, not because the cells contain more hemoglobin than physically possible. This higher density is often caused by a reduction in the red blood cell’s surface area relative to its volume, indicating a change in cell shape.
The most notable cause of hyperchromia is hereditary spherocytosis, a genetic disorder where red blood cells are spherical instead of the typical biconcave disc shape. These spherocytes have a smaller volume but retain a normal amount of hemoglobin, artificially driving up the calculated concentration. High MCHC can also occur in autoimmune hemolytic anemia, where the body mistakenly attacks its own red blood cells, or following severe thermal injuries. In some instances, a falsely high MCHC can be an artifact of the testing process, such as when red blood cells clump together due to conditions like cold agglutinin disease.