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    MCHC
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    MCHC

    MCHC — mean haemoglobin concentration in red cells (32–36 g/dL): low in iron deficiency, high in spherocytosis or artefact.

    Mean corpuscular haemoglobin concentration (MCHC) is the average concentration of haemoglobin inside red blood cells, expressed in g/dL (or g/L). Unlike MCH, it does not depend on cell size: it shows how densely the cells are packed with haemoglobin. MCHC varies little in health. A low value is typical of established iron deficiency. A high value is rare and suggests hereditary spherocytosis, other conditions with dense red cells, or a laboratory artefact.

    Complete blood countRed cell indicesSpherocytosis
    Adults32–36 g/dL
    CalculationHb / haematocrit × 100
    Lowiron deficiency, thalassaemia
    High (> 36)spherocytosis or artefact

    How MCHC is obtained

    MCHC (g/dL) = haemoglobin (g/dL) / haematocrit (%) × 100. For example, haemoglobin 14 g/dL and haematocrit 42 % give an MCHC of about 33 g/dL. Haemoglobin is already highly concentrated in red cells, close to the physical limit for keeping cells flexible. Values above about 37 g/dL are therefore uncommon, and they should prompt a check for artefact.

    MCHC scale with low zone below 32 grams per decilitre, normal 32 to 36 and high zone above 36, with typical causes Mean corpuscular haemoglobin concentration (g/dL) Low Normal High 3236 • Established iron deficiency• Thalassaemia• Sideroblastic anaemia • Hereditary spherocytosis• Sickle-cell disease (HbSC)• Artefact: cold agglutinins, lipaemia
    Figure 1. MCHC is tightly regulated; deviations are less frequent than with MCV and MCH but can be diagnostically useful.

    Reference values

    A common adult reference range is 32–36 g/dL (320–360 g/L). Clinical Methods gives 34 ± 2 g/dL. Ranges differ slightly between analysers.

    Low MCHC

    A low MCHC (hypochromia) usually appears in more advanced iron deficiency, after MCV and MCH have already fallen. It is also seen in thalassaemia and sideroblastic anaemia. In a blood smear the red cells look pale with a widened central pallor.

    High MCHC

    • Hereditary spherocytosis — an inherited defect of the red cell membrane. The cells lose surface area and become small, dense spheres that are destroyed in the spleen. It causes anaemia, jaundice, gallstones and an enlarged spleen.
    • Autoimmune haemolytic anaemia with spherocytes, severe burns, some haemoglobin variants (HbSC, HbCC)
    • Artefacts — cold agglutinins (red cells clump in a cold sample), lipaemia, haemolysis in the tube. The laboratory can repeat the test after warming the sample.
    When to see a doctor

    Discuss the result if MCHC is abnormal together with anaemia, yellowing of the skin or eyes, dark urine, tiredness or an enlarged spleen, or if there is a family history of spherocytosis or haemolytic anaemia.

    References

    1. Sarma PR. Red cell indices. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Boston: Butterworths; 1990. Chapter 152. ncbi.nlm.nih.gov/books/NBK260
    2. MedlinePlus. RBC indices. U.S. National Library of Medicine. medlineplus.gov/ency/article/003648.htm
    3. Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;372(19):1832–1843. doi:10.1056/NEJMra1401038

    This article is for general information and does not replace a consultation with a doctor. Laboratory results must be interpreted by a physician together with symptoms and other tests.

    Published on 11 February 2020