Erythrocyte Indices: What They Are For, Normal Values ​​

The í indices erythrocyte  are a summary of studies done with a whole blood sample to determine the condition of the red series, which is the cell corresponding to the erythrocytes or red blood cell line. The first laboratory test that every patient is asked for is usually a complete hematology or hematic biometry.

This study looks at the three basic cell lines in the blood: white blood cells (leukocytes), red blood cells ( erythrocytes ), and platelets (thrombocytes). The results for each group of cells can be interpreted individually or together.

Red blood cell indices

What is it for?

Erythrocyte indices help the doctor and his team to elucidate the etiology and characteristics of anemias.

Through these studies, the differential diagnosis between the different anemic pictures can be made, in addition to performing routine controls on patients with said disease.

They are also useful for diagnosing other types of hemoglobinopathies and hematological diseases, even those of a malignant nature that affect or modify the values ​​of the red blood series.

Primary red cell indices

They are semi-quantitative values ​​provided by the laboratory equipment in which the whole blood samples are processed, using methods such as impedance, laser counting or light diffraction. They are the first hematic biometry results to be reported and include:

– Hemoglobin.

– Hematocrit.

– Total number of erythrocytes.

– Reticulocytes.

Direct analysis of these indices makes it possible to determine the presence of anemia or polycythemia.

Secondary red cell indices

They are calculated based on the primary indices and guide the physician regarding the characteristics, etiology, and possible treatment of anemias. These include:

– Mean corpuscular volume (MCV).

– Mean corpuscular hemoglobin (HCM).

– Mean corpuscular hemoglobin concentration (MCHC).

Medium corpuscular volume

Defines the average red blood cell or erythrocyte size in a specific blood sample. It is expressed in fentoliters or cubic microns.

It is calculated using the following formula:

MCV = hematocrit (%) x 10 / total number of erythrocytes

Mean corpuscular hemoglobin

It refers to the amount of hemoglobin found within each erythrocyte or red blood cell. It is expressed in picograms. It is calculated through the formula:

HCM = Hb (gr / dL) x 10 / total number of erythrocytes

Mean corpuscular hemoglobin concentration

Indicates the average amount of hemoglobin per unit volume. Unlike mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration correlates hemoglobin content with erythrocyte size, making this value somewhat more accurate for certain diagnoses.

Its calculation is carried out with the following formula:

MCHC = hemoglobin (gr / dL) x 100 / hematocrit (%)

Normal values

The results of certain tests may vary according to the laboratory where they are performed and the equipment used. There are also modifications by race, gender, ethnicity, geographic origin, age and eating patterns that can be important.

The values ​​published in this text are those with the greatest acceptance and use worldwide, being broad due to the previous considerations.

Among the most important red cell indices we have:

Hemoglobin

11.5 – 15.5 gr / dL

Hematocrit

35 – 46%

Total number of erythrocytes

4.2 – 6.1 million cells per microliter (cel / mcL)

Reticulocytes

0.5 – 1.5%.

Mean corpuscular volume (MCV)

80 – 94 fentoliters (fL).

Mean corpuscular hemoglobin (HCM)

26-32 picograms (pg).

Mean corpuscular hemoglobin concentration (MCHC)

32 -36 g / dL

Red blood cell indices

Interpretation of results

Hemoglobin

Low hemoglobin levels indicate the presence of any type of anemia. Elevated levels of it signify polycythemia.

Despite being very nonspecific, this measure is essential for the initial diagnosis of any hematological pathology.

Hematocrit

It is the percentage of actual hemoglobin per unit volume. Associated with hemoglobin levels, it allows to know if hemoglobin values ​​have been affected by hemoconcentration (loss of fluids) or by hemodilution (increase in intravascular fluid).

Total number of erythrocytes

The total erythrocyte or red blood cell count is useful to determine if there is adequate red cell production or if it is decreased or increased. It can orient towards spinal or infectious problems although it is very unspecific.

Medium corpuscular volume

In the presence of an anemic condition, it helps to determine if there is normocytosis (red blood cell of adequate size), microcytosis (small red blood cell) or macrocytosis (large red blood cell). It is of vital importance to determine the etiology of anemias.

Examples of microcytic anemia

– Iron deficiency anemia (due to a decrease in iron in the body).

– Thalassemia minor.

– Sideroblastic anemia.

Examples of normocytic anemia

– For chronic diseases such as kidney failure, diabetes and liver disease (the most common in older adults).

– Hemolytic.

– Aplastic.

– Anemia due to malignant diseases.

Examples of macrocytic anemia

– Megaloblastic anemia (due to deficiency of vitamin B12 or folates).

Mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration

They help to identify if anemic pictures are normochromic, hypochromic or hyperchromic, thanks to the staining of the hemoglobin seen under the microscope.

Examples of hypochromic anemia

– Iron deficiency anemia.

Examples of normochromic anemia

– Hemolytic.

– Post-hemorrhagic anemia.

Examples of hyperchromic anemia

– Due to protein malnutrition.

– Aplastic anemia.

– Alcoholism.

– Thyroid diseases.

Reticulocytes

The reticulocyte count, an immature form of the erythrocyte, is useful in evaluating the production and quality of red blood cells. Some laboratory equipment calculates it automatically, and in some cases it must be specifically requested.

Faced with an anemic condition, the amount of reticulocytes allows us to classify it as regenerative or aregenerative and refers to the productive response of the bone marrow in a scenario of erythrocyte loss.

High reticulocytes = regenerative anemia. For example, hemolysis or acute bleeding.

Low reticulocytes = aregenerative anemia. For example, iron deficiency, aplastic anemia, or vitamin B12 or folate deficiency.

Polycythemia

Although erythrocyte indices guide us more in the diagnosis of anemias, we must not forget polycythemias. These blood diseases are characterized by the presence of an elevated hematocrit and, although rare, they must be considered.

Polycythemia vera or primary polycythemia is a bone marrow disease characterized by the exaggerated production of erythrocytes without there being a biological need for it. May be accompanied by an increase in white blood cells and platelets.

Other cases of polycythemia can be seen in dehydration, hypoxia, some types of cancer, immune diseases, and genetic disorders.

Another important cause is mountain sickness due to the decrease in available oxygen in the air at high altitudes, which causes a compensatory increase in hemoglobin in the blood.

References

  1. LabCE (2001). Red blood cells (RBC) indices: Definitions and Calculations. Recovered from: labce.com
  2. Ravi Sarma, P. (1990). Red Cells Indices. Clinical Methods: The History, Physical, and Laboratory Examinations, Third Edition, Chapter 152.
  3. Lopez – Santiago, N. (2016). Hematic biometry. Acta pediátrica de México, 37 (4), retrieved from: scielo.org.mx
  4. Torrens, Monica (2015). Clinical interpretation of the hemogram. Medical journal Clínica Las Condes,  26 (6), 713-725.
  5. Epstein, Judith and Cafasso, Jacquelyn (2017). RBC indices. Recovered from: healthline.com
  6. Naucapoma, Elena and Rojas, Giovanna (2005). Studies of red blood cell indices in the elderly. Cybertesis PERÚ Program,  retrieved from: cybertesis.unmsm.edu.pe
  7. MedBroadcast (last edition 2018). Polycythemia. Recovered from: medbroadcast.com

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