Hematocrit (PCV) & RBCs Indices PDF

HEMATOCRIT & RBC’s INDICES Packed Cell Volume of Whole Blood  Objectives 1. Determine hematocrit value of blood specimens manually in the lab. 2. Understand the principle of hematocrit determination. 3. List the mechanical and biological...

HEMATOCRIT & RBC’s INDICES Packed Cell Volume of Whole Blood  Objectives 1. Determine hematocrit value of blood specimens manually in the lab. 2. Understand the principle of hematocrit determination. 3. List the mechanical and biological factors that interfere with hematocrit determination. 4. State the clinical importance of the test. 2  PCV ◼ Hematocrit (PCV): the percentage of erythrocytes to the whole volume of blood.(vol/vol %). ◼ The hematocrit (PCV) is usually determined by spinning a blood-filled capillary tube in a hematocrit centrifuge. 3  Principle of the Test ◼ If whole blood is placed in a special hematocrit tube and then spun very rapidly in a centrifuge, the heavier component will quickly settle to the bottom of the tube. SO ….. ◼ When the centrifuge spins, the RBC’s are forced to the bottom of the tube, because they are the heaviest element in the blood 4  Principle of the Test ◼ The WBC’s and platelets are lighter, so they come to rest on top of heavier RBC’s in a layer called the Buffy Coat. ◼ Above the Buffy Coat rests the plasma. 5 PCV 6  MATERIALS 1) Blood specimen: ◼ venous blood anticoagulated with EDTA ,or capillary blood collected directly into heparinized capillary tubes can be used. ◼ specimens should be centrifuged within 6 hours of collection. ◼ Hemolyzed samples cannot be used for testing. 2) Capillary tubes: ( 75 mm long ) ◼ Heparinized for finger sticks (red tip). ◼ Plain for anticoagulated blood (blue tip). 7 PROCEDURE 8  MATERIALS 3) clay-type tube sealant. 4) Microhematocrit centrifuge. 5) Microhematocrit reader. 6) gauze. 7) Alcohol swab. 8) Lancet for capillary puncture. 9 PROCEDURE 10 PROCEDURE 11  PROCEDURE 1. Draw well-mixed anticoagulated blood into two microhematocrit tubes by capillary action avoiding air bubbles. ◼ The tubes should be filled about ¾ full. 2. Wipe off excess blood with a kimwipe or gauze. 12 PROCEDURE 13  PROCEDURE 3. Seal one end of each tube with a small amount of clay material at 90° angle. ◼ Be sure the seal has a perfectly flat bottom. 14 PROCEDURE 15  PROCEDURE 4. Place the filled and sealed capillary tubes into the centrifuge. ◼ The sealed ends should point toward the outside of the centrifuge. ◼ The duplicate samples should be placed opposite each other in order to balance the centrifuge. ◼ Record the position number of each specimen. 16 PROCEDURE 17  PROCEDURE 5. Securely fasten the flat lid on top of the capillary tubes. 6. Centrifuge for 5 minutes at a set speed (11000 rpm). ◼ This will separates the RBC’s from plasma and leaves a band of buffy coat consisting of WBC’s and platelets. 18 PROCEDURE 19  PROCEDURE 7. Allow the centrifuge to stop on its own. ◼ Do not use the hand brake. 8. After the centrifuge has stopped, open the top and remove the cover plate. 9. Promptly read the hematocrit reader. ◼ Do not include the buffy coat layer. ◼ If the buffy coat exceeds 2%,it should be recorded and noted as volume of packed WBC/plt. 20 PROCEDURE 21 PROCEDURE 22  Clinical Significant of The Test ◼ The PCV test : 1. It’s an easily measure for detecting anemia or polycethemia. 2. Useful in estimating changes in hemodilution or hemoconcentration. ◼ The PCV is used together with the RBC’s count ,in calculating the mean cell volume (MCV). 23  Clinical Significant of The Test ◼ Also the PCV is used together with hemoglobin content, in calculating the mean corpuscular hemoglobin concentration (MCHC). 24  Clinical Significant of The Test ◼ PCV is increased in: -- polycethemia: increased RBC’s count. a. pathological: bone marrow malignancy. b. physiological: - Age: (PCV is higher in infants). - Altitudes: (PCV is higher). ◼ PCV is decreased in: -- Anemia: decreased RBC’s count. 25  NORMAL VALUES ◼ Newborn : 53 – 65 %. ◼ Adult male : 42 – 52 %. ◼ Adult female : 37 – 47 %. 26  Mechanical Sources of Error 1. Incomplete sealing of the capillary tubes will give falsely low results. ◼ Because in the process of spinning ,RBC’s & small amount of plasma will be forced out from the tube. 2. The microhematocrit centrifuge should never be forced to stop by applying pressure to the metal cover plate. 27  Mechanical Sources of Error ◼ This will cause the RBC’s layer to sling forward & results in a falsely elevated value. 3. If the centrifugation time is too short or the speed is too low, an increase in trapped plasma (1- 3%) will occur in normal blood. ◼ Increased amount of trapped plasma can produce errors in cases where an erythrocyte abnormality exists, such as sickle cell anemia. 28  Mechanical Sources of Error 4. If too much time elapses between when the centrifuge stops and the capillary tube is removed, the red cells can begin to settle out and cause false reading of the hematocrit. 29  Biological Sources of Error 1. If the buffy coat is included in the RBC’s when reading the result, the hematocrit will be falsely elevated. 2. Hemolysis of the specimen can cause a falsely decreased result. 3. When the microhematocrit is spun for the correct time period and at the proper speed, a small amount of plasma still remains in the RBC’s portion. Is termed trapped plasma. 30  Biological Sources of Error ◼ So when we comparing spun microhematocrit results with hematocrit results obtained from an electronic cell counter, the spun hematocrit results are generally 1.3 – 3 % higher due to this trapped plasma. ◼ An increased amount of trapped plasma is found in: 1. Macrocytic anemias. 31 Biological Sources of Error 2. spherocytosis. 3. Thalassimia. 4. Hypochromic anemias. 5. Sickle cell anemia. 32  RBC’s INDICES There are 3 indices: 1. MCV = mean corpuscular volume. 2. MCH = mean corpuscular hemoglobin. 3. MCHC = mean corpuscular hemoglobin concentration. ◼ These indices are give indication about erythrocytes status and help in diagnosing type anemia. 33  MCV MCV : it is the volume of erythrocytes. Normal values : 80 – 100 fl (femtoliter). Formula : MCV = { PCV / RBC’s} x 10 PCV is in %. RBC’s is in millions/mm³. 34  MCV Terminology : If MCV between 80 to 100 fl. It indicates normal cell and the cell called normocyte which could be present in normal blood as well as normocytic anemias ,ex. Anemias caused by acute blood loss. If MCV is less than 80 fl. It indicates small-sized cell and the cell called microcyte which could be present in microcytic anemias ,ex. Iron deficiency anemia. If MCV is greater than 100 fl. It indicates large-sized cell and the cell called macrocyte which could be present in macrocytic anemias ,ex. Vitamin B 12 deficiency anemia 35  MCV ◼ Example : PCV = 45 % RBc’s count = 5000000/mm³. Then MCv = 45 / 5 X 10 = 90 fl. 36  MCH MCH : it is the amount of hemoglobin in one erythrocyte. Normal values : 27 – 32 pg (picogram). Formula : MCH = { Hb / RBC’s } x 10. Hb is in gm%. RBC’s is in millions/mm³. 37  MCH If MCH between 27 to 32 pg. It indicates normal cell and the cell called normochromic which could be present in normal blood as well as normochromic anemias ,ex. Anemias caused by acute blood loss. If MCH is less than 27 pg. It indicates abnormal cell and the cell called hypochromic which is present in hypochromic anemias , ex. Iron deficiency anemia. If MCH is greater than 32 pg. It indicates abnormal cell and the cell called hyperchromic which is present in hyperchromic anemias ,ex. Vitamin B 12 deficiency anemia 38  MCH ◼ Example : Hb = 15 gm /dl RBC’s = 5000000/mm³. Then MCH = 15 / 5 X 10 =30 pg. 39  MCHC MCHC : it is how much of the volume in one erythrocyte is occupied by hemoglobin. Normal values : 30 – 38 %. Formula : MCHC = { Hb / PCV } x 100. Hb is in gm%. PCV is in %. 40  MCHC If MCHC between 30 to 38 %. It indicates normal cell and the cell called normochromic which could be present in normal blood as well as normochromic anemias ,ex. Anemias caused by acute blood loss. If MCHC is less than 30 %. It indicates abnormal cell and the cell called hypochromic which is present in hypochromic anemias , ex. Iron deficiency anemia. If MCHC is greater than 38 %. It indicates wrong laboratory results because the erythrocyte cannot hold more than 38 % of its volume by hemoglobin ( ex. It is destroyed in the bone marrow ). 41  MCHC ◼ Example : Hb = 15 gm /dl PCV = 45 % Then MCHC = 15 / 45 X 100 = 30 %. 42  videos ◼ https://www.youtube.com/watch?v=BsOpOc- uf-0&ab_channel=vet.dr.ahmed ◼ https://www.youtube.com/watch?v=1SN_cmv sMto&ab_channel=atdove.org 43