Blood indices

Red blood cell indices, MCV,MCH,MCHC,RDW and CI

1. RED BLOOD CELL INDICES Dr. JILSHA

2. CONTENTS Introduction Mean corpuscular volume Mean corpuscular haemoglobin Mean corpuscular haemoglobin concentration. Red Cell Distribution width Colour Index

3. INTRODUCTION The values of Hemoglobin, Packed Cell Volume (PCV) and Total RBC count are used to calculate red cell volume and red cell hemoglobin content and concentration. These are called R ed B lood C ell indices.

4. INTRODUCTION The commonly estimated indices are : Mean Cell Volume (MCV) Mean Cell Hemoglobin (MCH) Mean Cell Hemoglobin Concentration (MCHC) Red Cell Distribution Width (RDW) Determination of these indices are is of considerable clinical importance and is widely used in the classification of anemia.

5. MEAN CORPUSCULAR VOLUME (MCV) MCV is the average volume of an RBC expressed in femtoliters (1 fL = 10-15 L). If the PCV and number of red cells per liter are known, MCV is calculated as follows :  

6. MCV The factor 10 is introduced to convert the hematocrit reading in % from volume of packed red cells per 100 mL to volume per liter. For example if the hematocrit is 40% and the red cell count is 5 million, then MCV is : = 80 fL  

7. MCV Normal value : MCV in adults in between 78 fL to 96 fL. APPLIED ASPECT MCV is the index of the size of red cells. It depicts whether the red cells are Microcytic, Normocytic or Macrocytic. If the MCV is less than 78 FL, the cells are microcytic . If it is greater than 96 FL, the cells are macrocytic.

8. MEAN CORPUSCULAR HEMOGLOBIN (MCH) MCH is the average weight of hemoglobin content in an RBC. It is expressed in picograms (1pg = 10 – 12 g) It is calculated as follows :  

9. MCH For example, if the hemoglobin content is 14 g/dl and the RBC count is 5 million: = 28 pg. Normal value : Normal range is 27 – 33 pg   APPLIED ASPECT MCH will be as high as 50 pg in macrocytic anemia or as low as 20 pg or less in microcytic hypochromic anemia

10. MEAN CORPUSCULAR HEMOGLOBIN CONCENTRATION (MCHC) It is the average hemoglobin concentration per unit volume of packed red cells. It is expressed as g/dl or percent.  

11. MCHC For example, if the Hb concentration is 15 g/dl and PCV is 45 % Normal value : between 33-37 g/dl or %   APPLIED ASPECT MCHC above 40% indicates error in instrument or manual method as 37% is the limit for hemoglobin solubility . In hypochromic anemias , the Hb concentration is reduced and values as low as 20 – 25% are present .

12. RED CELL DISTRIBUTION WIDTH (RDW) It is a measurement derived from the RBC distribution curve generated on automated hematology analyser and is an indicator of variation in RBC size within a blood sample. It is used along with other indices to describe the population of RBCs.

13. RDW It is calculated as follows : It is expressed in percentage. Normal range is 11-15%  

14. COLOUR INDEX (CI) It refers to the ratio of Hb to RBC. For calculating CI, Hb of 14.8 g/dl is taken as 100% and RBC count of 5 million/mm 3 is taken as 100 % For eg ., if Hb is 14.8 g/dl and RBC count is 4.5 million/mm 3 then 4.5*100 = 90%, so, CI = 100/90 = 1.11