Laboratory medicine precision

The essential criteria for a useful analytical technique are specificity, sensitivity, accuracy, precision, simplicity, rapidity, economy, wide applicability, and freedom from hazard. It is well known that radioimmunoassay (RIA) was developed in 1959 by Yalow and Berson (Yl). Since then the radioimmunoassay method has been widely used in the field of clinical chemistry. Radioimmunoassay has inherent in it the advantages listed above. However, this method always requires special facilities for use and disposal of radioisotopes and consideration must be given to the fact that the labeled substances have short half-lives. Immunoassay methods are explosively increasing in use and development as an analytic technique in basic science as well as in clinical laboratory medicine (L1-L3, VI). With these points as background, efforts have been made to develop nonisotopic immunoassay methods or alternative immunoassay methods that are based on antigen-antibody reactions but do not involve use of a radioisotope. 

The realisation that every laboratory determination that is carried out is associated with both random and systematic errors has had a major impact on laboratory medicine in the last thirty years. It is also at the heart of quality control and quality assurance procedures which are primarily concerned with understanding the sources of such errors and their suppression or minimisation (Whitehead, 1977 Aitio, 1981 Taylor, 1987). However, it has been pointed out by Broughton (1983) that all laboratories may carry out some form of "quality control" but this is often designed to give retrospective reassurance rather than provide prospective action. The dual concepts of bias and precision in laboratory medicine are well known, but not always appreciated even by users of reference materials (Taylor. 1985 Taylor, 1987). By definition an unbiased result should be the "true" result, but in practice this is hardly ever achieved. The nearest approach to a true value is generally obtained by using a certified reference material and a definitive method, but these ideals are unobtainable in the case of most trace metal analyses. 

Metal complexes of stable carbenes—or more precisely metal complexes of car-benes that are now known to be stable—have developed from laboratory curiosities to widely used compounds. The basis for this development was laid by Wanzlick s and Ofele s discoveries in the 1960s, the recent revival has certainly been driven by Arduengo s first isolation of an A-heterocyclic carbene in 1991, and the result is a permanently increasing number of synthetic routes towards precursors for stable carbenes, towards stable carbenes themselves, and their metal complexes. Simultaneously with their accessibility, the applicability of these compounds to various fields such as homogeneous catalysis, materials science, medicinal and bioinorganic chemistry has been evaluated. 

Because buffer solutions are widely used in the laboratory and in medicine, prepackaged buffers having a variety of precisely known pH values are commercially available (Figure 16.5). The manufacturer prepares these buffers by choosing a buffer system having an appropriate pKa value and then adjusting the amounts of the ingredients so that the [base]/[acid] ratio has the proper value. 

At the beginning of this decade we developed an aminocarbonylation [62, 63] method using Mo(CO)6 as the carbon monoxide source [64,65] with the intention of applying this reagent in laboratory-scale medicinal chemistry. A more precise goal was to enable fast generation of new amido-decorated HIV-1 protease inhibitors. The idea was that the microwave-promoted bis-... 

The early 1960 s saw the introduction of flame atomic absorption spectrometry (AAS) to clinical laboratories and this provided a sensitive yet simple analytical technique for the estimation of some trace elements in biological fluids. Trace elements is now perhaps an inaccurate description for those metals previously detectable in only small amounts when using older and less sensitive analytical techniques. Many such elements can now be estimated with precision and this has proved a great stimulus to trace-element research in clinical medicine. The number of trace elements known to be essential to man has doubled in the last twenty years [1]. Specific and treatable diseases are now known to be associated with excess or deficiency of trace elements and even in advanced societies dietary intake of some elements may be less than ideal [2]. Thus, monitoring of biological fluids for trace element levels in both health and disease can contribute towards major advances in nutritional management. 

As new types of procedures, increased test sensitivity, and therapeutic alternatives become increasingly available, the challenge will be to skillfully combine medicine, laboratory expertise, and analytical thinking in the guiding of laboratory practice. Maximizing benefits given a limited set of resources requires a weU considered approach to the selective improvement of test accuracy and precision and to the interpretation of test results. 

At this point, it is convenient to state precisely the position that Pharmacy occupied in the continental section of Western Europe. The pharmacists were the successors to the apothecaries of previous centuries. The strict regulation of the professions, separated into distinct corporations, had been beneficial for the scientific role of the apothecaries they were to limit their activity to the preparation and sale of medicinals, all accessory commerce being forbidden. The preparation of medicinals necessitated some knowledge of chemistry and botany. It was also necessary to perform the chemical manipulations at the dispensary and to be concerned with the gathering of local medicinal plants. This is the reason that, from 1750 to 1850, many naturally occurring compounds were isolated in the laboratories of the retail pharmacists. 

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