Immunodiagnostics and Patient Safety (eBook)

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Krystyna Sztefko, Jagiellonian University, Krakow, Poland.

Contents 6
Preface 10
Abbreviations 12
Part I – Immunoassay: Theory, practice, and patient safety 14
1 Immunochemical methods – Basic principles and definitions 16
1.1 Antibody as immunoassay reagent 16
1.2 Antigen as immunoassay reagent 20
1.3 The course of the immunochemical reaction 20
1.4 Immunoassay formats 22
1.5 Labels in immunochemical reactions 27
1.6 Separation of bound and unbound fractions 27
1.7 Other technologies based on the antigen-antibody reaction 28
1.8 Basic theory of immunoassay and patient safety 29
2 Immunoassay standardization 30
2.1 Reference materials for small molecules 30
2.2 Reference materials for proteins 31
2.3 Reference methods 32
2.4 Reference methods for heterogeneous proteins 33
2.5 Traceability 33
2.6 The uncertainty of measurement 34
2.7 Epitope as a solution for better standardization 36
2.8 Harmonization of immunoassays 37
2.9 Immunoassay standardization and the patient’s safety 37
3 Immunoassay calibration and calibration curve fitting 40
3.1 Calibration process 40
3.2 Commutability problem 41
3.3 Matrix effect 41
3.4 Calibration and patient safety 42
4 Reference intervals and immunoassay 44
4.1 General problems with reference intervals for analytes measured by immunoassay 44
4.2 Limitation of different approaches to reference intervals 45
4.3 Reference intervals and patient safety 46
5 Laboratory preanalytical and analytical phase of immunoassay 48
5.1 Laboratory preanalytical factors and immunoassay 48
5.2 Blood collection devices 49
5.3 Anticoagulants 50
5.4 Hemolysis, lipemia, hyperbilirubinemia, paraproteinemia, and immunoassay 50
5.5 Analyte stability in fresh and frozen serum samples 51
5.6 Analytical phase in immunoassay measurement 53
6 Human natural antibodies and immunoassay 56
6.1 The human immune system 56
6.2 Chemical structure of immunoglobulins 57
6.3 Antigen-combining site and complementarity-determining regions 58
6.4 Genes for immunoglobulin variable regions 59
6.5 Diversification of immunoglobulins in vivo 60
6.6 Natural antibody against exogenous (nonself ) and endogenous (self ) antigens 61
6.7 Natural antibodies and patient safety 64
7 Immunoassay interference – How to recognize, eliminate, or reduce it 66
7.1 Definition and prevalence of interference in immunoassay 66
7.2 Cross-reactivity versus interference in immunoassay 67
7.3 Analyte specific and nonspecific binding proteins as a source of interference in immunoassay 72
7.4 Autoantibodies as a source of interference 76
7.5 Nonimmune IgG complexes as a source of interference 79
7.6 Interference from heterophilic antibodies 82
7.7 Detection of heterophilic antibodies in the patient’s sample 91
7.8 Methods used for removal or inactivation of interfering heterophilic antibodies 102
7.9 High-dose effect (hook effect, prozone effect) 105
7.10 Low-dose hook effect 108
7.11 Interference from heterophilic antibodies and patient safety 109
7.12 Interpretation of immunoassay results is an art 110
8 Immunoassay and patient safety 116
8.1 Fallibility of immunoassays 116
8.2 Know your immunoassay 118
8.3 Basic knowledge on critical points in immunoassay for physicians 123
8.4 Immunoassay in research 126
8.5 Who is responsible for the patient’s safety? 126
Part II – Immunochemistry measurements in practice: Examples of problems in some current immunoassays 128
Example 1 Parathyroid hormone (PTH) – Heterogeneity as a major problem in PTH measurement by immunochemistry 130
Example 2 Human chorionic gonadotropin (hCG) – Problems of heterogeneity and lack of standardization 136
Example 3 Troponin measurement by immunoassay – Problem of low assay sensitivity and interference from heterophilic antibodies 142
Example 4 Aldosterone and proteolytic renin activity (PRA) – Are they useful together? 150
Example 5 Thyroglobulin measurement – Autoantibody problem 154
Example 6 Prolactin measurement by immunoassay – Heterogeneity and macroform problems 158
Example 7 Thyroid function tests – Most frequently measured and most difficult to interpret: Reference interval for thyroid-stimulating hormone (TSH) and problems of free thyroid hormone fraction measurement 162
Index 174