Endogenous Interferences in Clinical Laboratory Tests (eBook)

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Martin H. Kroll, Boston University, Massachusetts, USA; Christopher R. McCudden, University of Ottawa, Ontario, Canada; University of North Carolina at Chapel Hill, USA.

Preface 7
1 Accuracy Goals for Laboratory Tests 13
1.1 Accuracy and Precision 13
1.1.1 Definition 13
1.1.2 Imprecision as a Form of Error 14
1.2 Types of Error 14
1.2.1 Bias 14
1.2.2 Impact of Bias 16
1.3 Interference as a Type of Bias 18
1.4 References 20
2 Nature of Interferences 23
2.1 Definition 23
2.2 Nature of Interferences 23
2.3 Instrumentation 24
2.4 The Chemistry of the Absorbance of Light 27
2.5 References 32
3 The Nature of Icteric Interference 33
3.1 Source Information on Bilirubin Interference 33
3.2 Allen Correction as a Source of Bilirubin Interference 33
3.3 Bilirubin Interference with Oximetry 34
3.3.1 Co-oximetry Interference 36
3.3.2 Pulse Oximetry 37
3.3.3 Cerebral Oximetry 38
3.3.4 Interference with Methemoglobin 39
3.4 Chemical Reactions as a Cause of Bilirubin Interference 40
3.4.1 Bilirubin Reaction with Creatinine Methods 41
3.4.2 Bilirubin Reactions with Peroxidase Methods 43
3.5 References 44
4 The Nature of Lipemic and Turbidity Interferences 47
4.1 Types of Interferences 47
4.2 Lipemia Causes Turbidity 48
4.3 Lipemia Interference Mechanisms 49
4.3.1 Light Scattering 49
4.3.2 Lipoprotein Particles 52
4.3.3 Intralipid® and Lipemia Simulation 54
4.3.4 Empirical Studies in Lipemia Turbidity 55
4.4 Lipoprotein Particles and Lipemia 56
4.5 References 57
5 Measurement of Interference 59
5.1 A Typical Commercial Study 59
5.2 Guidelines for Interference Studies 60
5.3 Bilirubin 61
5.4 Intralipid® 62
5.5 Procedure to Make Five Concentrations 64
5.6 Interference Criteria 64
5.7 Data Analysis 66
5.8 References 72
6 Origin of Icteric Samples 75
6.1 The Origin of Bilirubin 75
6.2 Bilirubin Toxicity 77
6.3 Transport of Bilirubin in the Blood 77
6.4 Uptake of Bilirubin by the Liver 78
6.5 Clinical Aspects of Bilirubin 78
6.6 Neonatal Jaundice 79
6.7 Cholestasis 81
6.8 Hepatitis 82
6.9 Alcoholic Liver Disease 82
6.10 Hemolysis 83
6.11 Drug Induced Hyperbilirubinemia 83
6.12 Summary 84
6.13 References 84
7 Impact of Icterus 87
7.1 Introduction 87
7.2 Estimated Impacts Based on Interference Studies 87
7.3 Differential Interference with Different Bilirubin Isoforms 89
7.4 Non-spectrophotometric Icterus Interference 91
7.5 Resolving Icterus Interference 92
7.6 Summary 93
7.7 References 93
8 Origin of Lipemia and Turbidity 95
8.1 Lipoprotein Pathways 95
8.2 Classification of Hypertriglyceridemia 97
8.2.1 Frederickson Classification of Dyslipidemias 97
8.2.2 Obesity, Metabolic Syndrome and Diabetes 99
8.2.3 Alcohol 100
8.2.4 Nonalcoholic Fatty-liver Disorder 101
8.2.5 Medications 101
8.2.6 HIV Infection 101
8.2.7 Renal Disease 102
8.3 References 103
9 Impact of Lipemia/Turbidity 105
9.1 Introduction 105
9.2 Estimated Impacts Based on Interference Studies 107
9.2.1 Interference by Light Scattering 107
9.2.2 Interference by Volume Displacement 108
9.2.3 Interference by Lipid Partitioning 111
9.3 Summary 111
9.4 References 111
10 Endogenous Interferences in Clinical Laboratory Tests: Icteric, Lipemic and Turbid Samples 113
10.1 Interference Indices 113
10.2 Generating Interference Indices 113
10.2.1 Preparation of Standards 114
10.2.2 Data Collection and Deconvolution of Non-Target Interferences 115
10.2.2.1 Subtraction Using Selected Wavelengths 116
10.2.2.2 Index Calculation Using Derivative Spectrometry 117
10.2.3 Establishing Indices and Defining Ranges 119
10.3 Limitations 122
10.4 Summary 122
10.5 References 123
11 Reporting of Results 125
11.1 Introduction 125
11.2 Procedures for Handling Samples with Interference Within the Laboratory 125
11.3 Reporting of Results in Icteric and Turbid Samples 127
11.4 Autoverification and Reporting Algorithms 128
11.5 Practical Issues: Education and Implementation 129
11.6 References 130
12 Analyte-dependent Interference 131
12.1 Complex Interferences 131
12.1.1 Model for Analyte-dependent Interference 132
12.1.2 Examples of Analyte-Dependent Interference 133
12.2 Statistical Testing for Significance 141
12.3 Failure to Design the Interference Study 145
12.4 Advantages of Using Multiple Regression Analysis 145
12.5 Concluding Remarks 147
12.6 References 149
Index 151