Red Blood cell Indices

Sample for Red Blood cell Indices

1. For Blood indices, the best sample is EDTA blood.
2. Collect the blood in the lavender top tubes.
3. Transport the blood to the lab where blood is run in the hematology analyzer for the calculation of blood indices.
4. Blood is stable for 6 hours at 25 °C and for 24 hours at 4 °C.
5. Fetal blood is collected percutaneous from the umbilical area.

Purpose of the test (Indications) for Red Blood cell Indices

• These tests are useful for the diagnosis of the various types of Anemia.

Precautions for Red Blood cell Indices

1. The abnormal size of RBC may affect indices.
2. An increased count of WBC will affect the indices.
3. Increased reticulocytes count leads to abnormally high MCV.
4. Cold agglutinins give false increased values of MCH, MCHC, and MCV.

Definition of Red Blood cell Indices

• Red cell indices define the size and contents of hemoglobin in Red cells.

Mean corpuscular volume (MCV):

Definition of MCV:

1. This is the best index for classifying anemia.
2. This is the average volume of red blood cells measured in cubic micrometers (µ³, femtoliter fL).
3. This indicates the cell size of RBCs.

Indication of MCV:

1. It helps in the classification and differential diagnosis of anemia.
2. It is a useful screening test for occult alcoholism.

Interference of various factors for MCV:

1. In the case of leucocytosis, there is increased MCV.
2. Marked hyperglycemia increases MCV.
3. Cold antibodies increase MCV.
4. Methanol poisoning increases MCV.
5. In the case of increased reticulocytes, there is increased MCV.
6. Hemolysis leads to a decrease in MCV.

Calculation of MCV:

• MCV is calculated by dividing hematocrit by the total RBC count.

Normal MCV

• Adult (all ages) = 80 to 95 fL
• Newborn = 96 to 108 fL

On the basis of MCV:

1. Macrocytes when MCV value is high, e.g., in Megaloblastic anemia, due to vit B and folic acid deficiency.
2. Microcytes, when the MCV is decreased seen in iron deficiency anemia and thalassemia.
3. In microcytic anemia, MCV is 50 to 82 fL.
4. In normochromic normocytic anemia, MCV is 82 to 98 fL.
5. In macrocytic anemia, MCV is 100 to 150 fL (>100 fL).
6. In normocytic anemia = MCV 80 to 94 fL  MCHC >30 g/dL.

Mean corpuscular hemoglobin (MCH):

Definition of MCH:

1. This is the mean of the average amount of hemoglobin in red blood cells or the average weight of hemoglobin in absolute units in the RBCs.
2. The result gives the average hemoglobin content per RBC in picograms (pg).
3. The MCH value is usually higher in newborns and infants because their MCV is higher than that of adults.

Calculation of MCH:

• MCH is calculated by multiplying Hb g/dl x 10 and dividing by the RBC count.

• Generally, macrocytes will have more hemoglobin, and microcytes will have less hemoglobin. So the values resemble those of MCV.

Indications of MCH:

1. It has limited value in the differential diagnosis of anemia.
2. It is instrument calibration.

Interference for estimation of MCH:

1. Increased white cell count increases the MCH value.
2. Cold agglutinins increase the MCH value.
3. Lipemia increases the MCH value.
4. High concentrations of heparin increase the MCH value.
5. Monoclonal immunoglobulin increases the MCH value.
6. In vivo hemolysis increases the MCH value.

Normal MCH

• Adult (all ages) = 27 to 31 pg
• Newborn = 32 to 34 pg

Mean corpuscular hemoglobin concentration (MCHC):

Definition of MCHC:

1. This is the average concentration or percentage of hemoglobin in each individual red blood cell.
   1. It is the ratio of the weight of hemoglobin to the volume of the RBCs.
2. MCHC is the most useful for monitoring the treatment of anemia.

Indication of the MCHC:

1. It is better than MCH to identify hypochromasia.
2. Changes in the MCHC appear late in iron deficiency anemia (severe cases).
3. It is instrument calibration.

Calculation of MCHC:

1. This is calculated by hemoglobin x 100 divided by hematocrit.
2. It is the average amount of Hemoglobin per RBcs (33 to 37 g/dL).

Normal MCHC

• Adults of all ages = 32 to 36 g /dl (32 to 36%)
• Newborn = 32 to 33 g /dl (32 to 33%)

Interpretations of MCHC:

1. Hypochromic When MCHC is decreased, there is a hemoglobin deficiency, e.g., in iron deficiency anemia and thalassemia.
2. Normochromic when the values are normal (In hemolytic anemia).
3. Hyperchromic when MCHC value is increased, and RBC cannot accommodate more than 37 g/dl (seen in spherocytosis, newborns,s and infants).

Red blood cell distribution width (RDW):

Definition of RDW:

1. RDW is the quantitative measure of anisocytosis.
2. This is the coefficient of the RBC volume distribution.
3. This indicates variation in the size of RBC.
4. This is calculated by the machine using MCV and RBC values.
5. This is helpful for the diagnosis of hematological disorders and monitoring the response to therapy.
6. This is also helpful in distinguishing iron-deficiency anemia (RDW increased) from hemoglobinopathies (RDW normal).

Indications for RDW:

1. RDW is used to classify the anemias based on MCv and RDW.
2. RDW is more sensitive in microcytic than macrocytic RBC conditions.
3. RDW is not helpful in cases without anemia.

Calculation of RDW:

Normal RDW

• Adult = 11.5% to 14.5%

Anemias are defined based on cell size (MCV), amount of Hb, and (MCH):

Parameter	Interpretation	Diagnosis
MCV fL	Less than the lower limit of normal	Microcytic  anemia
	Within normal range	Normocytic anemia
	Greater than the normal	Macrocytic anemia
MCH pg	Less than the lower limit of normal	Hypochromic anemia
	Within the normal limit	Normochromic anemia
	Greater than the upper limit of normal	Macrocytic anemia

Classification of anemia on the basis of MCV and MCHC:

Type of anemia	MCHC%	MCV fL	Causes
Normocytic/normochromic	32 to 36	80 to 100	From blood loss Sepsis Tumors Aplastic anemia Prosthetic heart valve
Microcytic/hypochromic	<32	<80	Iron deficiency Lead poisoning Thalassemia
Microcytic/normochromic	32 to 36	<80	Due to a deficiency of erythropoietin from kidney failure
Macrocytic/normochromic	32 to 36	>100	Chemotherapy Folate deficiency Vitamin B12 deficiency Hydantoin therapy

MCV:

MCV Increased in:

1. Pernicious anemia (vit B12 deficiency or folate deficiency).
2. Folic acid deficiency.
3. Antimetabolite treatment.
4. Chronic liver disease.
5. Alcoholism.
6. Sprue likes steatorrhea, celiac disease, and intestinal resection or fistula.
7. Fish tapeworm infestation.
8. Carcinoma of the stomach following total gastrectomy.
9. Drugs like oral contraceptives, anticonvulsants, anti-tumor agents, and antimicrobial agents.
10. Anemia of hypothyroidism.
11. Postspenectomy.
12. Myelodysplastic syndrome.

MCV Decreased in:

1. Microcytic anemia where MCV <80 fL and MCHC <30 g/dL).
2. Iron deficiency anemia.
3. Thalassemia.
4. Chronic diseases.
5. Iron deficiency anemia is usually seen in inadequate iron intake, poor absorption, and chronic blood loss.
6. Sideroblastic anemia.
7. Anemia of chronic diseases.
8. Lead poisoning.
9. Disorders of porphyrin synthesis.

MCV normal in:

1. Normocytic anemia.
2. Some hemolytic anemia.
3. In some hemoglobinopathies.
4. Hypoplastic and aplastic marrow.

MCH:

MCH Increased in:

1. Macrocytic anemias.
2. Newborn.

MCH Decreased in:

1. Microcytic anemias.
2. Hypochromic anemia.

MCHC:

MCHC Increased in:

1. Spherocytosis.
2. Newborns and infants.

MCHC Decreased in:

1. Iron deficiency anemia.
2. Thalassemia.
3. Microcytic anemia with chronic blood loss.

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