Критерії вибору методу дослідження

В. І. Цвіліховський, В. А. Томчук

Анотація


 

STUDY SELECTION CRITERIA METHOD

V. Tsvilikhovskyi, V. Tomchuk

 

The right choice of research method in diagnostic laboratories is one of the main issues of chemical analysis. From economic, analytical and diagnostic point of view, it plays an important role in organizing the work of the laboratory. Therefore, the criteria for choosing a method, the correctness and accuracy of measurements, the provision of laboratory analytical equipment is always relevant in the laboratory analysis.

The purpose of the research was to assess the criteria for choosing a research method in biochemical laboratories for organizational, analytical and diagnostic points of view.

The research materials were accepted common analytical methods and scientific publications in the field of laboratory diagnostics.

Each of the methods can be considered from several points of view: organizational, analytical, and diagnostic. Organizational issues include: conditions for the implementation of the method (toxicity), labor costs, additional training of personnel, the purchase of new equipment, reagents, ensuring the safety of the method, the possibility of transporting and storing research biomaterials and conducting quality control at the preanalytical stage. Organizational issues include the cost of reagents and equipment, salaries of staff. From analytical point of view, the method characterizes sensitivity and specificity; accuracy and reproducibility, availability of standard samples, control materials, the possibility of quality control at the analytical stage. These also relate to the stability of reagents and the number of interfering in the reaction of substances. The diagnostic significance of the method is determined by sensitivity and specificity, the ability to obtain the result in the shortest possible time, organization of standardization and external quality control, including control and post-analytical stage.

The choice of one or another method is justified by economic considerations. The high cost of reagents, the need for special equipment hinders the widespread adoption of the method, especially in small-sized laboratories. There are other obstacles. Thus, the cost of reagents for the determination of glucose by the ferricyanide method is low, there is no need to use optical equipment, but its use is not justified due to the labor intensity and duration. In small laboratories it is possible to determine glucose using the orthotoluidine method, but in large laboratories it is expedient to use glucose oxidase method. Reference laboratories should also use the hexokinase method.

At choosing a method of definition, there are often conflicts between organizational problems, analytical capabilities of the method and diagnostic aspects, so a compromise solution is needed. Thus, the necessity of an express method for performing a method does not always satisfy the sensitivity and specificity of the clinical diagnostic analysis. The high quality of the implementation of the express method contradicts the high definition cost. The use of micro-volumes of biological material often results in the use of methods that do not differ in high sensitivity and accuracy. The presence of a photoelectrocolorimeter in a laboratory only causes the use of spectrophotometry in the visible spectral region. The desire to have diagnostically important data on the activity of the organism-specific isoenzymes is contrary to the high cost of their determination.

The high cost of research is one of the main reasons for the slow introduction into practice of new technology. The presence in the laboratory of automated equipment allows conducting diagnostic researches in a short interval of time, but using of biochemical autoanalyzers does not guarantee getting of high-quality results.

Accuracy depends mainly on the calibration procedure. When working with autoanalysers for this purpose, calibrators are used – lyophilized blood serum, in which the content of the substance is determined by reference or coordinated methods. The use of calibrators makes it possible to compare the determination of a substance in a standard sample and the analyzed sample under identical conditions.

At implementing a new diagnostic method, the following should be assessed: expected number of inquiries, availability of reagents, equipment, consumables, calibrators, standard samples and control materials in the laboratory, the need for personnel training, quality control, commercial kits, their cost. Everything fully applies to the development of new methods of pharmacokinetics immunoassay for our laboratories. The desire to adjust pharmacokinetic tests leads to the need to choose the principle of polarization – fluorescence (immunochemical method) or high-performance liquid chromatography. In the first case, it is possible to use commercial sets of reagents and specialized equipment, but it should take into account the high cost of kits and standard samples, limited storage time, closed analytical system. The choice of high-performance liquid chromatography allows the use of commonly used equipment, the definition becomes much cheaper, but in this case, the laboratory should have highly skilled personnel.

Ideal method is to mix a simple stable reagent containing inexpensive ingredients with a microobjective of a biological sample and quickly obtaining a stable and reproducible optical density value at photometry in the visible spectral region. The method must have an analytical specificity, do not depend on temperature, have linearity in the range of normal and pathological values. However, for one analyst there is currently no such method that would have all the advantages.

The questions of choice criteria of research method in diagnostic laboratories are considered according to organizational, analytical, diagnostic and economic point of view extend the horizons of scientists and laboratory assistants of diagnostic laboratories in the field of choice of the method of biochemical analysis, correctness and accuracy of measurements, provision of laboratory with analytical equipment.

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