RBC INDICES final.pptx

Rbc details

1. RBC INDICES Presented by- Dr. Sangita Jha Moderator- Dr. Sheetal mam

2. CONTENT INTRODUCTION RBC INDICES-DEFINITION AND CALCULATION APPLICATION OF RBC INDICES IN VARIOUS DISORDERS SUMMARY REFERENCE

3. OBJECTIVES To define and calculate the RBC Indices. To describe the application of RBC Indices in diagnosing various disorders.

4. RBC INDEX It is a quantitative measurement of red blood cell, the amount and concentration of haemoglobin in them. They were first introduced by Wintrobe in 1929 to define the size (MCV) and haemoglobin content (MCH & MCHC) of red blood cells. More recently Red cell Distribution Width (RDW) has been included

5. DEFINITION: MEAN CELL VOLUME (MCV) It is the measure of average volume of RBCs MEAN CELL HEMOGLOBIN (MCH) It is a measurement of the average weight of haemoglobin in individual erythrocytes

6. DEFINITION: MEAN CELL HEMOGLOBIN CONCENTRATION (MCHC) It is the average concentration of haemoglobin in erythrocytes in a decilitre of erythrocytes. RED CELL DISTRIBUTION WIDTH (RDW) It is a measure of variability of erythrocyte size.

7. WHY RBC INDICES ARE REQUIRED? To classify the erythrocytes by their volume and Haemoglobin content. The indices suggest how the RBC would look microscopically and provide significant information. (Most commonly for Anaemia diagnosis) Laboratory professionals correlate the indices with haematocrit ( Hct ), haemoglobin levels and RBC count to ensure that technical problems are identified when they occur.

8. MEAN CELL VOLUME It is the average size of the red cells. MCV = PCV in % X 10 . RBC count ( 10 12 /L ) in million/ cmm MCV is expressed in femtoliters or fl (10 -15 of a liter). MCV is a measurement of volume whereas estimation of size of flattened cells is a measurement of cell diameter. Cell diameter and volume are not same.

9. Normocytic : 80-100 fl Microcytic : Red cells with reduced volume (< 80 fl ) Macrocytic: Red cells with an increased volume ( >100 fl ) Thus eg , if the PCV is 0.45(i.e. 0.45 litres of red cells per litre of blood) and the RBC is 5 x 10 12 = 90 femtolitres( fl ) Volume of 1 cell =0.45 /5 x 10 12 = 90 femtolitres MEAN CELL VOLUME

10. MCV VALUES AND DIFFERENT TYPES OF ANAEMIA Decreased ( microcytic; low MCV) Normal(normocytic; normal MCV) Increased(macrocytic; high MCV) Iron deficiency anaemia Acute blood loss Megaloblastic anaemia Lead poisoning Anaemia of chronic disease Hypothyroidism Sideroblastic anaemia Enzyme defects(eg.G6PD deficiency) Liver disease Thalassemia Acute haemolysis Folic acid deficiency

11. MEAN CELL HAEMOGLOBIN(MCH) Average amount of haemoglobin in a single red cell. MCH= Haemoglobin in grams/dl X 10 Red cell count in millions/ cmm MCH is expressed in picograms or pg. Reference range is 27-32 pg.

12. MEAN CELL HEMOGLOBIN MCH increases in B12 deficiency Folic acid deficiency Haemolytic anaemia Alcoholism MCH decreases in Iron deficiency anaemia Thalassemia Anaemia of chronic disorder

13. MEAN CELL HAEMOGLOBIN CONCENTRATION(MCHC) Concentration of haemoglobin in 1 dl or 1 litre of packed red cells Expressed in grams/dl or grams /litre MCHC= Haemoglobin in grams/dl PCV in % Reference range is 30-35 grams/dl

14. MEAN CELL HAEMOGLOBIN CONCENTRATION(MCHC) MCHC corresponds with degree of haemoglobinization of red cells on a blood smear If MCHC is normal, red cell is normochromic If low, red cell is hypochromic MCHC is raised in HEREDITARY SPHEROCYTOSIS and is decreased in hypochromic anaemia.

15. RED CELL DISTRIBUTION WIDTH The RDW is derived from pulse height analysis and can be expressed either as standard deviation (in fl ) or as the coefficient of variation (CV)(%). Current Beckman-Coulter and Bayer- Technocon instruments express the RDW as the SD, and Sysmex instruments express it as either the SD or the CV.

16. RED CELL DISTRIBUTION WIDTH-CV The RDW expressed as the CV helps in distinguishing between: Iron deficiency(RDW usually increased) Thalassemia trait (RDW usually normal) Megaloblastic anaemia (RDW often increased) Other causes of macrocytosis (RDW more often normal)

17. RED CELL DISTRIBUTION WIDTH-CV Normal value : 11.5 – 14.5 % Increased value indicates ANISOCYTOSIS. Combination of low MCV and high RDW is one of the best screening test for the Iron deficiency anaemia

18. RED CELL DISTRIBUTION WIDTH-SD The determination of RDW-SD is an actual measurement of the width of the erythrocyte distribution curve. This measurement is performed at a relative height of 20% above the baseline. The wider the curve is spread by erythrocytes of different sizes, the higher the RDW-SD value will be. Reference values-35-45fl.

19. APPLICATION OF RED CELL DISTRIBUTION WIDTH The RDW is a red cell measurement that quantitates cellular volume heterogeneity reflecting the range of red cell sizes within a sample RDW is proposed to be useful in early classification of anaemias as it becomes abnormal earlier in nutrition deficiency anaemias especially iron deficiency anaemia

20. APPLICATIONS OF RED CELL DISTRIBUTION WIDTH RDW is also useful in identifying red cell fragmentation, agglutination or dimorphic cell populations(including patients who have had transfusions, sideroblastic anaemias or have been recently treated for a nutritional deficiency)

21. DIFFERENTIAL DIAGNOSIS OF ANAEMIAS BASED ON MCV AND RDW MCV RDW CAUSES 1. NORMAL HIGH Early Iron Deficiency Anaemia 2. LOW HIGH Iron deficiency anaemia 3.LOW NORMAL Thalassemia 4. NORMAL NORMAL Anaemia of chronic disease, hereditary spherocytosis 5. HIGH HIGH Megaloblastic anaemia , Immune haemolytic anaemia

22. LIMITATIONS OF RBC INDICES Though the test for RBC INDICES is cost effective and simple, it has its own limitations. Such as, It is a screening test not a diagnostic test. MCV is not reliable when Anisocytosis is present. In dimorphic anaemia again MCV is not reliable. MCV does not reflect the diameter of the RBC, it is a volume of RBC. False high or false low value which should be evaluated further.

23. LIMITATIONS OF RBC INDICES RDW as a major variable has limited utility as they are not specific in separating heterozygous thalassemia from iron deficiency anaemia alone , since to conclude parameters like iron and haemoglobin studies would still be needed.

24. SUMMARY RBC index (MCV , MCH, MCHC) and RBC count helps in diagnosis of anaemia. Combination of various RBC indices (MCV , MCH, and MCHC) especially with RDW is useful in differential diagnosis of anaemia.

25. REFERENCES Mc Kenzie SB, Williams JL.Clinical laboratory haematology.3 rd edition.New jersey:Pearson education inc;2015 Lippincott Williams & Wilkins,Wintrobe’s clinical haematology.Twelfth edition,2009 Frank Firkin,Colin Chesterman, David Penington & Brian Rush. De Gruchy’s clinical haematology.5 th edition, Australia, 2003 Bain BJ,Bates I,Laffan MA,Dacie and Lewis SM,Practical haematology.11 th edition.Netherlands:Elsevier;2012