16 Principles of clinical biochemistry
J. FYFFE AND K. WILSON
16.1 Principles of clinical biochemical analysis
16.2 Clinical measurements and quality control
16.3 Examples of biochemical aids to clinical diagnosis
16.4 Suggestions for further reading
16.5 Acknowledgements
16.1 PRINCIPLES OF CLINICAL BIOCHEMICAL ANALYSIS
16.1.1 Basis of analysis of body fluids for diagnostic, prognostic
and monitoring purposes
Underlying most human diseases is a change in the amount or function of one or more
proteins that in turn triggers changes in cellular, tissue or organ function. The dysfunc-
tion is commonly characterised by a significant change in the biochemical profile of
body fluids. The application of quantitative analytical biochemical tests to a large range
of biological analytes in body fluids and tissues is a valuable aid to the diagnosis and
management of the prevailing disease state. In this section the general biological and
analytical principles underlying these tests will be discussed and related to the general
principles of quantitative chemical analysis discussed in Section 1.3.
Body fluids such as blood, cerebrospinal fluid and urine in both healthy and diseased
states contain a large number of inorganic ions and organic molecules. Whilst the
normal biological function of some of these chemical species lies within that fluid, for
the majority it does not. The presence of this latter group of chemical species within the
fluid is due to the fact that normal cellular secretory mechanisms and the temporal
synthesis and turnover of individual cells and their organelles within the major organs
of the body, both result in the release of cell components, particularly those located in
the cytoplasm, into the surrounding extracellular fluid and eventually into the blood
circulatory system. This in turn transports them to the main excretory organs, namely
the liver, kidneys and lungs, so that these cell components and/or their degradation
products are eventually excreted in faeces, urine, sweat and expired air. Examples of
cell components in this category include enzymes, hormones, intermediary metabolites
and small organic and inorganic ions.
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