11_Hema_I_Chapter_11_RBC_indices.ppt hematology

Hematology

1. CHAPTER 11: RED
CELL INDICES

2. Objectives
At the end of this chapter, the student will be able to:
Define MCV, MCH and MCHC.
Explain the purpose of calculating the red cell indices
Calculate MCV, MCH and MCHC values from given
values
Define RDW
Discuss the clinical significance of RDW

3. Outline

4. 11.1. Introduction
The red cell indices:
are absolute values calculated from:
 the measured hemoglobin,
PCV
RBC count
are of considerable clinical importance in the diagnosis
and classification of anemias
are dependent upon the accuracy of the various red
cell parameter estimations

5. Introduction cont’d
The red cell indices include
Mean corpuscular volume (MCV)
Mean corpuscular hemoglobin (MCH)
Mean corpuscular hemoglobin concentration
(MCHC)
Red cell distribution width (RDW) is another important
red cell parameter obtained by electronic methods
RDW measures the variation in size of the red blood
cells (degree of anisocytosis)
It must be remembered that the red cell count has the
greatest potential error and must be performed with
extreme care preferably using an electronic counter

6. 11.2.The Mean Cell Volume (MCV)
 Is the average volume of a red cell expressed in femto
litres (fL)
Femtoliter is 10
-15
of a liter
MCV is obtained by dividing the PCV by red cell number
 MCV (fl) = PCV (l/l)
No. of RBC/L
Example: PCV = 0.45(l/l)
RBC = 5  10
12
/l
MCV = 0.45 (l/l) = 90  10
-15
= 90fl
5  10
12

7. Interpretation
Normal Values
Men and Women: 80-100 fl
MCV
 increased in
 macrocytic anemias
decreased in
iron deficiency anemia
Thalassemia
microcytic anemia

8. 11.3. The Mean Cell Hemoglobin (MCH)
is the average amount of hemoglobin per individual red
cell expressed in picograms (pg).
It is given by:
MCH (Pg) = Hb (g/L)
RBC/L
Example: Hb conc. = 150g/L
RBC = 5  10
12
/L

MCH (pg) = 150 = 30  10
-12
= 30pg
5  10
12

9. Interpretation
Normal Value: Men and women: 27-31 pg
MCH is increased in
macrocytic anemia
MCH is decreased in - microcytic anemia
- iron deficiency anemia

10. 11.4 The Mean Cell Hemoglobin Concentration
(MCHC)
-Is the average hemoglobin per unit volume of red cells.
MCHC (g/l) = Hb (g/L)
PCV (L/L)
Example: Hb conc. = 148g/L
PCV = 0.45 (L/L)
MCHC = 148 = 328g/L
0.45

11. Interpretation
Normal Values: Men and women: 32-36 % (320-360
g/L)
MCHC is increased in some cases of hereditary
spherocytosis
MCHC is decreased in iron deficiency anemia

12. 11.5. Red Cell Distribution Width (RDW)
Another index, the red cell distribution width (RDW), is
specifically designed to reflect the variability of red cell
size.
It is based on the width of the red blood cell volume
distribution curve
 larger values of RDW indicate greater variability.
 An elevated RDW may be an early sign of iron-
deficiency anemia

13. RDW cont’d
proposed as an aid in distinguishing iron deficiency from
other causes of microcytic anemia, such as thalassemia,
 the RDW is not sufficiently specific to obviate the need
for more specific tests.
 The RDW can be used in the laboratory as a flag to
select those samples submitted for automated blood
count that should have manual review of the blood film
for red cell morphology

14. RDW cont’d
In the Coulter Model S plus, for example, a red cell
histogram is plotted and the RDW(%) is defined as the
coefficient of variation of the MCV:
RDW (%) = SD of MCV x 100
Mean MCV
The reference range for RDW is from 11% to 15%, but
varies with the instrument used.

15. Review Questions
1.Define: MCV, MCH, MCHC, and RDW.
2.What is the purpose of calculating the red cell indices?
3.A complete blood count was performed for a patient and
the following profiles were recorded:
WBC= 8,000/mm
3
PCV = 50%
Hb = 15g/dl
RBC count = 5 x 10
6
/mm
3
Calculate the MCV, MCH and MCHC values for the
patient. Interpret your results in the light of the normal
values for these indices.