Hematocrit (Hct)

What sample is needed for Hematocrit (Hct)?

1. The patient’s blood is taken in EDTA.
2. It is stable for 48 hours at 4 °C and 6 hours at 23 °C.
3. Fetal blood:
   1. Collected by percutaneous blood sampling.

What are the precautions for Hematocrit (Hct)?

1. The test should be performed within 6 hours of blood collection.
2. EDTA is the choice of blood anticoagulant.
3. Avoid hemolysis.
4. Avoid clotting of the blood.
5. Centrifugation must be adequate. This will give a high result.
6. The buffy coat is not included in the hematocrit.
7. Avoid excess EDTA.
8. Avoid overdilution of the blood sample by the anticoagulant.
9. Avoid prolonged tourniquet use; it can lead to hemoconcentration and errors in Hct.
10. Drugs like penicillin and chloramphenicol decrease the Hct level.

What are the Indications for Hematocrit (Hct)?

1. It is used to diagnose anemia.
2. Hct is done in patients with bleeding or blood loss.
3. It is part of a complete blood count.

How will you define hematocrit (Hct)?

• After the centrifugation of the EDTA blood in the test tube.
• It is also called packed cell volume.
• The % of RBCs in the original whole blood volume is called hematocrit (Hct).

What is the principle of hematocrit (Hct)?

1. The word hematocrit means to separate blood into plasma and blood cells.
2. This test provides information on RBC concentration and helps assess hemoconcentration.
3. This is a measure of total blood volume and the RBC ratio as a percentage.
4. In a capillary tube or Hct tube, blood is centrifuged.
   1. Cells, mainly RBCs, will settle down, and clear plasma will appear on top.
   2. This ratio of settled cells and upper clear plasma is calculated in %.

How will you calculate Hematocrit (Hct) by Hemoglobin?

1. This hemoglobin quality control can be done by checking Hb results in g/dL and comparing the result with hematocrit results.
2. Hct results in % units, using the following formula:

3. One g/dL Hb  unit = 3 Hct unit
   1. For example, if the Hb is 13 g/dL
   2. Then Hct is = 13 x 3 = 39 %
4. Now, compare the result with the Hct value.

What Factors Will Affect Hematocrit (Hct)?

1. Abnormalities of RBC morphology will affect Hct.
2. Raised WBC values will alter the Hct.
3. People from high altitudes have increased Hct.
4. After the hemorrhage, the values are unreliable.
5. Dehydration and hemodilution will affect the Hct.
6. Pregnant ladies will have low values due to hemodilution.
7. Chloramphenicol and Penicillin decreased in value.

How will you discuss the pathophysiology of Hematocrit (Hct)?

1. Hct is a macroscopic parameter measured as the percentage volume of packed RBCs.
   1. This is also called the packed cell volume (PCV).
   2. The Hct closely reflects the hemoglobin and RBC values.
   3. Hct mostly depends upon the number of RBCs
2. Hematocrit means to ‘separate blood’, where blood cells and plasma are separated by centrifugation.
3. Meanwhile, it is calculated by MCV in electronic counters.
4. A calculated Hct is lower than 2% than the microhematocrit due to trapped plasma in a centrifuged RBC column.
5. Hct is lower in pregnant women than in nonpregnant women.
   1. Females have less Hct than men.
6. Hct is usually three times the Hb concentration in grams/dl.
7. Decreased values indicate anemia.
8. Increased values indicate erythrocytosis.
   1. In dehydration, Hct will be falsely high due to less plasma volume, and the number of RBCs is the same.
   2. In the case of large-sized RBCs, the Hct will be falsely high.
9. Blood transfusion is not recommended if the Hb is >8 g/dl or Hct is >24 %.
10. Hct is more reliable and useful than the RBC count.
11. Serial hematocrit estimation:
    1. Serial hematocrit estimation may be used once every 2 to 4 hours to indicate blood volume changes.
    2. It usually takes roughly 2 hours after an acute bleeding episode for a significant change (drop) in the hematocrit.
    3. Occasionally, it may take more time, from 6 to 12. hours.
    4. When there is greater extracellular blood loss, the hematocrit changes sooner. In this case, this may be >2%.
12. In case of dehydration:
    1. It will delay the drop of hematocrit.
13. In the case of low plasma protein:
    1. In the low plasma protein, the hematocrit drop is late.

How will you perform the Hematocrit (Hct) procedure?

1. Microhematocrit tube method. These are as correct as the tube method.
2. The Wintrobe hematocrit method is the macro method.
3. Automated method.
   1. In an automated machine, the RBC count and MCV are calculated.
   2. Hb = RBC in a million x 3
   3. Hct = Hb x 3
   4. Hct = RBC in a million x 9
   5. This formula depends upon the value of MCHC (33).
      1. This factor varies depending on the MCHC from 2.7 to 3.2.

 What is the normal Hematocrit (Hct)?

Source 2

Fetal Hematocrit (Hct) level:

Source 4

Hematocrit (Hct) level at various ages:

What is the significance of Hematocrit (Hct)?

1. Decreased values indicate Anemia.
2. Decreased values are also seen in Leukemia, Lymphoma, Hodgkin’s disease, and Myeloproliferative disorders.

What are the causes of increased Hematocrit (Hct)?

1. Polycythemia Vera.
2. Erythrocytosis.
3. Extreme physical exercise or excitement.
4. High Altitude.
5. Dehydration leads to Hemoconcentration, e.g., diarrhea, burns, and vomiting.
6. Congenital heart failure.
7. Severe chronic pulmonary obstructive disease (COPD).

What are the causes of decreased Hematocrit (Hct)?

1. Anemia.
2. Hemoglobinopathies.
3. Cirrhosis.
4. Hemolytic anemia (Erythroblastosis fetalis, drug-induced hemolytic anemia, and paroxysmal nocturnal hemoglobinuria.
5. Hemorrhage.
6. Bone marrow failure
7. Renal diseases.
8. Normal pregnancy.
9. Autoimmune diseases.
10. Malignancies like lymphoma, leukemia, multiple myeloma, and Hodgkin’s disease.
11. Normal pregnancy.
12. Bone marrow failure.

What is the critical value of Hematocrit (Hct)?

• Critical value of Hct = Low =  <15 % 
•                                             High = >60 %.

Questions and answers: