EKSPRESS-METODY of laboratory diagnosis

From Big Medical Encyclopedia

EXPRESS METHODS of laboratory diagnosis — the methods of the accelerated carrying out laboratory analyses allowing during from several seconds to 10 — 15 min. to define the presence of any substrate or quantitative deviations at its contents having diagnostic value in the studied biological material. Objects of the emergency laboratory researches usually are blood, urine, sometimes cerebrospinal liquid, strip exudate, emetic masses, kcal. The accelerated technology is implemented also in tsitol. researches, especially during the carrying out an urgent biopsy (see) fabrics during surgery.

To the middle of 20 century for the emergency diagnosis only nek-ry traditional laboratory methods which were not demanding considerable expenses of time were used. Since the 50th E. - m of laboratory diagnosis began to develop hl. obr. on the basis of two directions scientific tekhniche sky progress: in connection with development and deployment in practice a wedge. laboratories of the automated systems accelerating a research morfol. and biochemical composition of blood and urine (see Avtoanalizatora), and on the basis of the achievements of chemistry and the chemical industry which provided a possibility of production of so-called rapid tests the litmus paper used for an express method of definition of acid or alkali reaction of the environment was a prototype to-rykh.

Modern rapid tests present themselves sets of chemical reactants in the form of tablets, granules, powders or the strips of filter paper containing reactants, with the help to-rykh it is possible to define existence of various chemical components in biol. liquids (the so-called qualitative test) or approximately to estimate their quantitative maintenance (the so-called semi-quantitative test). Tablets, granules and powders are usually intended for definition of any one component, i.e. are monotests. The paper strips containing reactants have several indicator zones, i.e. represent the polytests allowing to receive results on five and more than parameters of chemical composition at the same time.

AA. - the m which are carried out by means of rapid tests are based on the chemical reactions, known from classical methods of the analysis, in to-rykh interaction of substrate and a reactant is followed by formation of connections with a certain coloring. Or on an indicator zone of a paper strip apply the studied liquid (more often the strip is immersed in liquid) on a tablet and on time of emergence of coloring, on intensity of color or size of the painted zone judge existence or lack of the studied substance. Comparison of intensity of coloring of an indicator zone with color paper standards allows to estimate approximately the quantitative content of the defined substrate at liquids (a semi-quantitative method).

In blood serum determine the content of urea by reactive paper strips — semi-quantitative rapid tests of «Ureatest» (USSR) and Uranal (GDR); activity of the cholinesterase changing at poisonings with organophosphorous poisons, diseases of a liver, a myocardial infarction — «Indicator paper for definition of activity of cholinesterase» (USSR), «Biofan-S» (GDR). In whole blood determine the content of glucose — a semi-quantitative rapid test of Dekstronal (GDR). To number of the most widespread E. - m of a research of urine treat with use of rapid tests semi-quantitative methods of definition of Glyukotest glucose (USSR), «Biofan-2» (GDR), Glyukofan (ChSSR); qualitative and semi-quantitative methods of definition of acetone and ketone bodies by means of a special set of reactants (USSR), reagnost-atsetonreaktivny tablets (GDR), the ketofan - diagnostic strips (ChSSR); a semi-quantitative method of definition of protein by means of biofan-E-reaktivnoy bumagi (GDR); detection and semi-quantitative method of definition of impurity of blood tablets «Reagnost-gemoglobin» (GDR) or haemo fan indicator paper (ChSSR); detection of bilirubin and a semi-quantitative method of definition of urobilin in urine by means of reactive tablets (GDR) or UBG-fan-reaktivnoy bumagi (ChSSR); definition ascorbic to - you (Askofan, ChSSR); bacteriurias («Nitrifan», ChSSR). Use of polytests, such as Albufan (ChSSR) on protein and pH is perspective; «Biofan-3» (GDR) — on protein, glucose and pH; «Tetra-fan» (ChSSR) — on availability of deoxidizing substances, glucose, a squirrel; availability of the listed above substrates, and also ketones can be defined by the Penta-fan polytest (ChSSR).

For obtaining reliable results by means of rapid tests it is necessary to use the fresh well mixed urine, negemolizirovanny blood serum. At assessment of results comparison with a color scale should be carried out to the terms established by the instruction from the moment of the beginning of reaction; the color scale needs to be protected from influence of sunshine, contact with chemical substances. Reactive paper strips are sensitive to effect of moisture and heat therefore they are stored in close packing in the cool place, do not allow a touch fingers to zones of indication. Regular quality control of rapid tests by comparison of their results to data of other methods of laboratory researches is required.

In comparison with usual laboratory methods E. - the m based on use of rapid tests differ in a number of advantages.

1. Speed of the analysis, edge cannot be reached by the known methods of mechanization or automation of laboratory works and processes. So, definition of sugar in blood by means of Dekstronal indicator paper requires only 60 sec. 2. Simplicity of a research; it can be made by any doctor or the trained nurse. 3. Profitability; rapid tests can be applied without any service equipment, a lab. ware, optical and electronic devices. 4. Dry reactants are steadier than liquid, it is more compact, more convenient during the transportation and storages. At the same time qualitative rapid tests differ in high reliability, and semi-quantitative have quite adequate accuracy for diagnostic inferences.

AA. - m are necessary first of all in urgent cases for diagnosis of life-threatening states when results of the analysis need to be received urgently at a bed of the patient, in the conditions of a domiciliary care. They are especially important for intensive care units and resuscitation where there are regular or non-staff doctors and laboratory assistants providing the round-the-clock carrying out researches. Such laboratories, except biochemical rapid tests, carry out a wedge. blood tests (determination of quantity of erythrocytes, leukocytes. hemoglobin), define blood groups, a Rhesus factor, a blood clotting time, gematokritny number, an acid-base state, content in blood of electrolytes, investigate kcal on the occult blood, etc. Use of the modern express equipment allows to determine in a short space of time in one blood sample at the same time 10 parameters (and the result is given automatically on the printer), to establish by means of the selection electrodes the maintenance of ions of sodium, potassium, etc.

E. - the m based on uses of rapid tests are used in receptions of BC, in out-patient practice more and more widely, including at visit of patients with the doctor or paramedical staff at home. They can be applied also by the patients who are previously instructed, as introspection («pocket» laboratory), e.g., patients with a diabetes mellitus can determine by special paper strips of «Glyukotest» qualitative I the semi-quantitative content in urine of glucose. Rapid tests help with receptions of hospitals to sorting of the arriving patients, promote reduction of the period of inspection that allows to begin quicker the correct treatment, and as a result reduces terms of stay of the patient in a hospital.

In the course of transition to annual medical examination of all population use E. - the m considerably expands possibilities of skriniruyushchy inspections (see Screening in medicine), gives the chance to reduce number of labor-consuming laboratory researches by 3 — 4 times since need for quantitative biochemical researches for laboratories at the same time arises only in case of detection of pathology by express tests. E.g., at suspicion on a gargoilizm (see) availability of acid mucopolysaccharides in urine it can be installed by the simplified test with acid albumine, Bør's reactions with toluidine blue or on opacification of urine in reaction with cetylpyridinchloride (tsetvalony) in the citrate buffer that allows to reduce considerably number of labor-consuming researches by means of ion-exchange chromatography (see) and an electrophoresis (see) on paper or an atsetattsellyuloza.

Perspectives of development E. - m of laboratory diagnosis are connected with development and further improvement of systems of automation of laboratory researches, with creation of the new differentiated rapid tests for qualitative and quantification biol. materials, and also with improvement of laboratory engineering (see). One of the directions of development E. - the m is development I implementation of microexpress-methods, at to-rykh the most limited volume biol is used. liquids. So, the microexpress-method of definition of a prothrombin ratio reduces the volume of blood, necessary for the analysis, from 0,5 ml to 0,08 ml. Astrup's micromethod on the basis of rectilinear dependence between log pCO2 and pH of blood is developed for express diagnosis of disturbances of acid-base balance. Unlike a labor-consuming method of Van-Slayka (see Van-Slayka methods), Astrup's micromethod allows in 3 — 5 min. in 0,1 ml of capillary blood to define at the same time pH, rso2, surplus of the bases in whole blood, and also standard and true bicarbonates and the general carbonic acid of a blood plasma (see Acid-base equilibrium).

Bibliography: Ways of improvement of activity of clinical diagnostic laboratories, under the editorship of. In, V. Menshikova, page 79, M., 1976; Todorov Y. Clinical laboratory trials in pediatrics, the lane with bolg., Sofia, 1968; Beck C., Maurer H. - C. u. 811-bersiepe M. of Blutzuckerechnellbestimmung mit Dextrostix (Streifenteet), Med. Labor., Bd 20, 8. 88, 1967.

E. E. Gogin, G. V. Litvinenko.