Essential Guide to Blood Groups

Abbreviations x

1 An introduction to blood groups 1

What is a blood group? 1

Blood group antibodies 3

Clinical importance of blood groups 3

Biological importance of blood groups 3

Blood group systems 4

Blood group terminology and classification 4

2 Techniques used in blood grouping 8

Factors affecting antigen–antibody reactions 8

Temperature 8

Time and ionic strength 9

pH 9

Antigen density 9

Stages of haemagglutination reactions 10

Direct agglutination 11

Indirect agglutination 12

Enzyme techniques 12

Antiglobulin tests 14

Elution techniques 18

Automation of test procedures 19

Flow cytometry 19

Molecular blood group genotyping 21

3 The ABO blood groups 22

Introduction 22

ABO antigens, antibodies, and inheritance 22

A1 and A2 23

Antigen, phenotype, and gene frequencies 24

ABO antibodies 25

Importance of the ABO system to transfusion and transplantation medicine 26

Biochemical nature of the ABO antigens 27

Biosynthesis of the ABO antigens and ABO molecular genetics 28

H, the precursor of A and B 30

ABH secretion 31

H-deficient red cells 32

Further complexities 32

Acquired changes 33

Associations with disease and functional aspects 34

4 The Rh blood group system 35

Introduction – Rh, not rhesus 35

Haplotypes, genotypes, and phenotypes 36

Biochemistry and molecular genetics 37

D antigen (RH1) 40

Molecular basis of the D polymorphism 40

D variants 41

Clinical significance of anti-D 42

D testing 44

C, c, E, and e antigens (RH2, RH4, RH3, RH5) 44

Clinical significance of CcEe antibodies 45

Molecular basis of the C/c and E/e polymorphisms 45

Other Rh antigens 45

Compound antigens:: ce, Ce, CE, cE (RH6, RH7, RH22, RH27), and G (RH12) 46

Cw, Cx, and MAR (RH8, RH9, RH51) 46

VS and V (RH20, RH10) 46

Rh-deficient phenotypes – Rhnull and Rhmod 47

Putative function of the Rh proteins and RhAG 47

5 Other blood groups 49

The Kell system 49

The Kell glycoprotein and the KEL gene 49

Kell system antigens 50

Kell system antibodies 51

Ko phenotype 51

McLeod syndrome, McLeod phenotype, and Kx (XK1) antigen 52

The Duffy system 52

Fya (FY1) and Fyb (FY2) 52

Anti-Fya and -Fyb 53

Fy3 and Fy5 53

The Duffy-glycoprotein, a receptor for chemokines 53

Duffy and malaria 54

The Kidd system 54

Jka (JK1) and Jkb (JK2); anti-Jka and -Jkb 54

Jk(a-b-) and Jk3 55

The Kidd-glycoprotein is a urea transporter 55

The MNS system 56

M (MNS1) and N (MNS2); anti-M and -N 56

S (MNS3) and s (MNS4); anti-S and -s 56

S- s- U- phenotype and anti-U 57

Other MNS antigens and antibodies 57

The Diego system 57

Band 3, the red cell anion exchanger 57

Dia (DI1) and Dib (DI2); anti-Dia and -Dib 58

Wra (DI3) and Wrb (DI4); anti-Wra and -Wrb 58

Other Diego-system antigens 59

The Lewis System 59

Some other blood group systems 61

P1PK 61

Lutheran 61

Yt 61

Xg 61

Scianna 61

Dombrock 62

Colton 62

Landsteiner–Wiener (LW) 62

Chido/Rodgers 62

Gerbich 62

Cromer 63

Knops 63

Indian 63

I 63

JR and Lan 64

Vel 64

Antigens that do not belong to a blood group system 64

6 Clinical significance of blood group antibodies 65

Antibody production and structure 66

Factors affecting the clinical significance of antibodies 69

Antibody specificity 69

Haemolytic transfusion reactions (HTR) 71

Intravascular red cell destruction 72

Extravascular red cell destruction 72

Haemolytic disease of the fetus and newborn (HDFN) 73

Crossmatching for infants under 4 months old 75

Autoantibodies 77

Tests to assess the potential significance of an antibody 77

Decision-making for transfusion 78

7 Blood grouping from DNA 81

Fetal blood grouping 81

Blood group typing of patients and donors 82

Next generation sequencing 84

The future of blood group serology 84

8 Quality assurance in immunohaematology 85

Achieving total quality 85

Frequency and specificity of control material 86

Quality requirements for safe transfusion practice 88

Checklist of critical control points 89

Laboratory errors, root cause analysis (RCA), and corrective and preventive action (CAPA) 89

9 Trouble-shooting and problem-solving in the reference laboratory 92

ABO grouping 92

Rh grouping 94

Problems in antibody screening, identification, and crossmatching 95

10 Frequently asked questions 102

What is the difference between sensitivity and specificity and how can these be determined? 102

Why is anti-A,B no longer obligatory in ABO typing? 102

Why are two anti-D reagents often recommended for RhD typing? 103

What is the importance of detecting D variant (weak D and partial D) phenotypes? 103

How do I control the results for antiglobulin testing? 103

Why should RhD positive women be tested more than once during pregnancy? 104

How often should transfusion recipients be tested for the presence of antibodies? 104

How can passive anti-D be differentiated from anti-D due to alloimmunisation? 104

Why do we need to perform antibody screening? Isn’t a crossmatch by IAT at 37°C enough to detect
incompatible blood? 105

What is the incidence of alloimmunisation post-transfusion? 105

How do I determine and identify antibodies present in a sample? 105

What is a compound antibody? 105

How can the incidence of compatible donors for a recipient with multiple antibodies be calculated? 106

Why can’t the droppers in bottles of reagents be used instead of a volumetric pipette? 106

What cells should be used when performing an antibody titration? 107

How are the results of titrations reported? 107

What is a Major Obstetric Haemorrhage? 107

What is ‘Massive Transfusion’? 107

When group-specific blood is in short supply, how do I select the ‘next best’ for transfusion? 108

How are high-titre haemagglutinins classified? 108

What is an ‘immediate spin’ crossmatch? 108

What is an ‘electronic crossmatch’? 108

Which patients are not eligible for electronic issue of blood? 108

What is ‘bed-side’ testing? 109

What are signs and symptoms of a suspected transfusion reaction? 109

What action should be taken in the event of a suspected transfusion reaction? 109

In haemovigilance, how should ‘near-miss’ events be characterised? 109

Recommended reading and web sites 111

Index 113