Automated methods of clinical analysis

Biomedical analytical chemistry happens to be one of the latest disciplines which essentially embraces the principles and techniques of both analytical chemistry and biochemistry. It has often been known as clinical chemistry . This particular aspect of analytical chemistry has gained significant cognizance in the recent past by virtue of certain important techniques being included very much within its scope of analysis, namely colorimetric assays, enzymic assays, radioimmunoassays and automated methods of clinical analysis. 

Give a comprehensive account on the various automated methods of clinical analysis with an appropriate example. 

An automated system for clinical analysis consists of the instmment (hardware), the reagents, and the experimental conditions (time, temperature, etc) required for each deterrnination. The reagents plus the experimental conditions are sometimes referred to as the chemistry of the system. The chemistry employed is generally similar to that used in manual assays because most automated assay methods have been adapted from the manual ones. However, automated analy2ers rarely afford the flexibiUty of experimental procedure that is possible in manual analysis. 

Most of the problems which the clinical chemist has in separating solids from liquids in routine analysis are relatively easily solved by use of non-automated methods of filtration or centrifugation. Except for certain reagents which require filtering or centrifuging in bulk, the main problems from the standpoint of automation are that multiple, relatively small samples must be filtered or centrifuged in a manner which prevents one sample from contaminating another. 

Chemical kinetic methods of analysis continue to find use for the analysis of a variety of analytes, most notably in clinical laboratories, where automated methods aid in handling a large volume of samples. In this section several general quantitative applications are considered. 

The relative simplicity of the sensor setup allows them to be implemented into portable automated devices or bed-side analyzers (Fig. 4.2), which are easily installed at patient beds, eliminating the time-consuming laboratory analyses. On the other hand, modem high throughput clinical analyzers may process more than 1000 samples per hour and simultaneously determine dozens of analytes, using a handful of analytical methods. Blood electrolyte analysis, however, remains one of the most important in... 

The determination of quantity in complex mixtures is also vital in health care and medicine. We are all familiar with the medical examinations in which a sample of blood or urine is sent to a laboratory for analysis. The procedures used have been developed by chemists, and are performed by trained chemical technicians. The high level of automation achieved by the chemists who designed these analytical procedures has greatly reduced the costs of such analyses. Clinical analysis continues to be driven by a need for better methods to detect and measure important proteins, for example, that while present in tiny amounts are relevant to our health and well-being. 

Further progress of ECL probes immobilization methods should result in new robust, stable, reproducible ECL sensors. Especially, the use of electrochemilumi-nescent polymers may prove to be useful in this respect. There are also good prospects for ECL to be used as detection in miniaturized analytical systems particularly with a large increase in the applications of ECL immunoassay because high sensitivity, low detection limit, and good selectivity. One can believe that miniaturized biosensors based on ECL technology will induce a revolution in clinical analysis because of short analysis time, low consumption of reactants, and ease of automation. 

There are four basic system types. Type I are basic isocratic systems used for simple, routine analysis in a QA/QC environment often for fingerprinting mixtures or final product for impurity/yield checking. Type II systems are flexible research gradient systems used for methods development, complex gradients, and dial-mix isocratics for routine analysis and standards preparation. They fit the most common need for an HPLC system. Type III systems are fully automated, dedicated systems used for cost-per-test, round-the-clock analysis of a variety of gradient and isocratic samples typical of clinical and environmental analysis laboratories. Type TV systems are fully automated gra-... 

In this regard, our laboratory demonstrated a method for the quantification of STI571 and its main metabolite, CGP 74588, in human plasma using a semi-automated PPT method and a relatively rapid LC/APCI/MS/MS analysis. The assay exhibited an excellent linearity from 4.00 to 10,000 ng/mL in human plasma. The method was utilized for the analysis of thousands of clinical samples. Furthermore, the method was routinely amenable to analysis of STI571 and CGP 74588 in cerebrospinal fluids (CSF), gastrointestinal stromal tumor (GIST) biopsy specimens, and toxicokinetic studies (data not shown). 

The immunoassay is today a relatively well-established technique, with numerous applications in clinical analysis, but also with a considerable growing interest in other fields, such as the food industry or environmental monitoring. Benefits such as high selectivity and sensitivity (for certain analytes not attainable by any alternative methods), speed and relatively low cost of analysis have also led to rapid commercialization of immunoassay kits and automated analysers [4]. 

After amplification, tlie products can be detected by various methods. Simple gel electrophoresis with ethidium bromide staining may suffice. When greater accuracy is required, one of the primers can be fluorescently labeled so that after PCR the fragments are accurately sized on a DNA sequencing device. Alternatively, some form of hybridization assay can be used to verify or analyze the amplified product. Automated methods are always attractive and closed-tube methods are particularly advantageous in the clinical laboratory. Adding a fluorescent dye or probe before amplification allows thermocyclers equipped with optical detection to analyze the reaction as it progresses (real-time PCR) or after the reaction is complete (endpoint measurement) without need to process the sample for a separate analysis step. 

K5. Kessler, G., An automated system of analysis. In Gradwohl s Clinical Laboratory Methods and Diagnosis Frankel, S., and Reitman, S., eds.), Vol. 1, pp. 301-321. Mosby, Saint Louis, Missouri, 1963. 

---