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Practical PhysiologyPractical Physiology

55thth Lab. Lab.

Packed Cells VolumePacked Cells Volume

(PCV)(PCV)

Packed Cells VolumePacked Cells VolumePCVPCV

Measurement of hematocrit or packed cell Measurement of hematocrit or packed cell volume is the most accurate and simplest of all volume is the most accurate and simplest of all tests in clinical hematology for detecting the tests in clinical hematology for detecting the presence and degree of anemia or presence and degree of anemia or polycythemia. In comparison, hemoglobin polycythemia. In comparison, hemoglobin estimation is less accurate, and RBC count far estimation is less accurate, and RBC count far less accurateless accurate..

What is effect of high hematocritWhat is effect of high hematocrit??

Increase in hematocrit increase the viscosity of Increase in hematocrit increase the viscosity of blood which leads to an increase in peripheral blood which leads to an increase in peripheral resistance, and thus the blood pressure.resistance, and thus the blood pressure.

Normal values of PCVNormal values of PCV

At Birth 56 ± 10 %.At Birth 56 ± 10 %.

Adults male 47 ± 5 %.Adults male 47 ± 5 %.

Adult femaleAdult female 42 ± 5 %. 42 ± 5 %.

Increased in PCV is seen inIncreased in PCV is seen in

New born, high altitude, hypoxia, New born, high altitude, hypoxia, due to heart or lung disease, due to heart or lung disease, polycythemia.polycythemia.

All type of anemiaAll type of anemiaPregnancy Pregnancy

Decreased in PCV is seen inDecreased in PCV is seen in

Blood IndicesBlood Indices What the MCV MeansWhat the MCV Means MCV measures the average size of the MCV measures the average size of the

red blood cells.red blood cells. The MCV rises when red blood cells The MCV rises when red blood cells

are larger than normal (macrocytic). are larger than normal (macrocytic). This condition is called macrocytic This condition is called macrocytic anemia.anemia.

The MCV falls when red blood cells are The MCV falls when red blood cells are smaller than normal (microcytic). This smaller than normal (microcytic). This condition is called microcytic anemia.condition is called microcytic anemia.

When MCV values are normal, the red blood When MCV values are normal, the red blood cells are normal in size. They are called cells are normal in size. They are called normocytic. However, a person with normocytic. However, a person with normocytic red blood cells can still be anemic normocytic red blood cells can still be anemic when there are too few red blood cells or when when there are too few red blood cells or when other RBC indices are abnormal. This is called other RBC indices are abnormal. This is called normocytic anemia.normocytic anemia.

What the MCH MeansWhat the MCH Means MCH measures the average amount of MCH measures the average amount of

hemoglobin in a red blood cell.hemoglobin in a red blood cell. When MCH values are high, the red When MCH values are high, the red

blood cells are called hyperchromic. blood cells are called hyperchromic. The red blood cells will be deeper in The red blood cells will be deeper in color. This condition is called color. This condition is called hyperchromic anemia.hyperchromic anemia.

When MCH values are low, the red When MCH values are low, the red blood cells are called hypochromic. The blood cells are called hypochromic. The red blood cells will be paler in color. red blood cells will be paler in color. This condition is called hypochromic This condition is called hypochromic anemia.anemia.

When MCH values are normal, the When MCH values are normal, the red blood cells are normal in color. red blood cells are normal in color. They are called normochromic.They are called normochromic.

What the MCHC MeansWhat the MCHC Means

The MCHC is the average concentration The MCHC is the average concentration of hemoglobin inside a red blood cell. of hemoglobin inside a red blood cell. 

The MCHC is Hgb divided by the Hct. So The MCHC is Hgb divided by the Hct. So MCHC = Hgb/Hct.MCHC = Hgb/Hct.

When the MCHC is higher than normal, When the MCHC is higher than normal, then hemoglobin is abnormally then hemoglobin is abnormally concentrated in red blood cells. The red concentrated in red blood cells. The red blood cells will be deeper in color. This blood cells will be deeper in color. This is called hyperchromia.is called hyperchromia.

When the MCHC is lower than When the MCHC is lower than normal, hemoglobin is abnormally normal, hemoglobin is abnormally diluted in the red blood cells. The diluted in the red blood cells. The red blood cells will be paler in color. red blood cells will be paler in color. This condition is called hypochromic This condition is called hypochromic anemia.anemia.

When the hemoglobin concentration When the hemoglobin concentration is normal, the MCHC is normal.is normal, the MCHC is normal.

Normal ValueNormal Value

MCV: 80 to 100 femtoliterMCV: 80 to 100 femtoliter

MCH: 27 to 31 picograms/cellMCH: 27 to 31 picograms/cell

MCHC: 32 to 36 grams/deciliterMCHC: 32 to 36 grams/deciliter