Clinical chemistry tests, automated

Billions of tests are run annually in clinical chemistry laboratories automation has therefore played a large role there. In the preceding sections, automated process-control systems were described. The first part of the present section describes the needs of the clinical chemistry laboratory as they relate to automation. The remainder will be devoted primarily to how clinical instruments are automated and which instrumental methods are most commonly used. Selected instruments will be described. 

Clinical Chemistry Tests. The diversity of tests that the clinical chemistry laboratory may be called upon to perform is continually expanding. Very few older tests are displaced by the newer ones developed. A reasonably sized laboratory will be prepared to perform over 60 different tests routinely, and a regional reference laboratory will offer between 200 and 300. However, many of the latter are performed infrequently and do not justify automation. Table 24.2 lists the tests that have been commonly automated. 

Clinical chemistry, initiated in the 1940s. involves the biochemical testing of body fluids to provide objective information on which to base clinical diagnosis. The ever-increasing demand for high quality, routine clinical testing stimulated the development of automated techniques, and as early as the 1960s automation in the clinical laboratory was the rule rather than tlie exception. 

The principle approach to immunoassay is illustrated in Figure 1, which shows a basic sandwich immunoassay. In this type of assay, an antibody to the analyte to be measured is immobilized onto a solid surface, such as a bead or a plastic (microtiter) plate. The test sample suspected of containing the analyte is mixed with the antibody beads or placed in the plastic plate, resulting in the formation of the antibody—analyte complex. A second antibody which carries an indicator reagent is then added to the mixture. This indicator may be a radioisotope, for RIA an enzyme, for EIA or a fluorophore, for fluorescence immunoassay (FIA). The antibody-indicator binds to the first antibody—analyte complex, free second antibody-indicator is washed away, and the two-antibody—analyte complex is quantified using a method compatible with the indicator reagent, such as quantifying radioactivity or enzyme-mediated color formation (see Automated instrumentation, clinical chemistry). 

Dry tests and test strips described by Morris et al. (1987) and Litman (1985) contain all the reagents required for a quantifiable test on a strip or filter. Evaluation can be performed visually or be read-out by a pocket reflectometer. Automated systems for a higher sample throughput are also available. The sensitivity of these tests is rather low (mg- xg/mL range) but sufficient for application as quick tests in clinical chemistry. 

Ion-selective electrodes (ISEs) represent the current primary methodology in the quantification of S-Li [11-13], Moreover, ISE modules are parts of large and fully automated clinical chemistry analysers. In practice, the validation parameters are most often chosen in terms of judging the acceptability of the new measurement system for daily use. For this reason, the first approach was to study whether the detected imprecision fulfilled the desired analytical quality specifications. Secondly, proficiency testing (PT) results from past samples were of great value in predicting future bias. The identity of the three ISE methods was evaluated using patient samples. The analytical performance was checked after 6 months routine use. Without any exception, method validations always mean an extra economical burden. Therefore, the validation parameters chosen and processed have to be considered carefully. 

C) produced and reported its state-of-the-art S-Li results independently of Lab A and Lab B. In 1999, Lab A and Lab C fused to form one company. In the new laboratory union, the former Lab A was lacking an in-house S-Li test method, while the current instrumentation used for S-Li determinations was running out of its technical performance capabilities. Consequently, New Lab A (united Lab A + C) evaluated the production status in terms of S-Li and decided to set up a fully automated S-Li method within the capabilities of the available clinical chemistry automation and discontinue the subcontract with Lab B. 

Enzyme assays in fields other than clinical chemistry generally are not as automated because there is typically not the same demand for throughput there are notable exceptions in facilities that perform an extensive number of tests on animals. 

Automation in the clinical laboratory has been spurred by the steady rise in the number of tests, an annual growth rate of about 10%. As mentioned before, about two billion tests a year are performed in clinical chemistry laboratories in the United States. This could not be physically accomplished without some automation. 

Because the majority of tests in the clinical chemistry laboratory are colorimetrically based, the greatest effort toward automation has been with colorimetric methods. As previously discussed, most of the automation classifies as automatic rather than automated. 

The reasons for briefly discussing PBI techniques in this review are minimal except for the fact that many automated units are still operating and because a PBI determination is sometimes useful in conjunction with other tests in delineating the site of a biosynthetic block in thyroid hormone synthesis. The subject was last reviewed in the series Advances in Clinical Chemistry by Chaney (C6) in 1958, and probably the most recent review is by Acland in 1971 (A4). 

An important part of the chemical enterprise is the chemical analysis of human specimens, often called clinical chemistry. Our medical system depends tremendously on these clinical tests, which have been developed hy chemists over many years. Clinical chemists routinely handle human specimens, such as hlood, serum, plasma, urine, sahva, spinal fluid, or feces, to provide data that help physicians and other health care providers determine medical treatments. There are many hundreds of these types of analytical methods. Some are automated and some have to he performed individually hy a chemist or other trained professional. 

The task of integrating laboratory automation begins with the laboratory workstation. In general, a clinical laboratory workstation is usually devoted to a defined task (e.g., performing chemistry profiles, complete blood counts, hormone testing, polymerase chain reaction testing, and urinalysis) and contains appropriate laboratory instrumenta-... 

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