МИНИСТЕРСТВО ЗДРАВООХРАНЕНИЯ РЕСПУБЛИКИ БЕЛАРУСЬ УЧРЕЖДЕНИЕ ОБРАЗОВАНИЯ «ГРОДНЕНСКИЙ ГОСУДАРСТВЕННЫЙ МЕДИЦИНСКИЙ УНИВЕРСИТЕТ» С.В. Лелевич, В.В. Воробьев, Т.Н. Гриневич КЛИНИЧЕСКАЯ ЛАБОРАТОРНАЯ ДИАГНОСТИКА Пособие для студентов факультета иностранных учащихся с английским языком обучения S.V. Lelevich, V.V. Vorobiov, T.N. Grynevich CLINICAL LABORATORY DIAGNOSTICS Study guide for the Medical Faculty for International Students Гродно ГрГМУ 2013 УДК 616-07(075.8) ББК 53.45я73 Л 33 Рекомендовано Центральным научно-методическим советом УО «ГрГМУ» (протокол № 3 от 31.10.2012). Авторы: доц. каф. клинической лабораторной диагностики и иммунологии, канд. мед. наук С.В. Лелевич; доц. каф. клинической лабораторной диагностики и иммунологии, канд. мед. наук В.В. Воробьев; асс. каф. клинической лабораторной диагностики и иммунологии Т.Н. Гриневич. Рецензент: зав. 2-й каф. внутренних болезней, канд. мед. наук В.И. Шишко. Лелевич, С.В. Л 33 Клиническая лабораторная диагностика : пособие для студентов факультета иностранных учащихся с английским языком обучения (на англ. яз.) / С.В. Лелевич, В.В. Воробьев, Т.Н. Гриневич = Clinical laboratory diagnostics / S.V. Lelevich, V.V. Vorobiov, T.N. Grynevich. – Гродно : ГрГМУ, 2013. – 100 с. ISBN 978-985-558-165-0 This manual provides information on some issues of clinical laboratory diagnostics. Data on laboratory evaluation of renal functional state are given; questions of clinical hematology, laboratory hemostasis system evaluation are discussed as well as a number of clinical studies. The manual is intended for the students of the Medical Faculty for International Students. УДК 616-07(075.8) ББК 53.45я73 ISBN 978-985-558-165-0 © Лелевич С.В., Воробьев В.В., Гриневич Т.Н., 2012 © УО «ГрГМУ, 2013 2 CONTENTS INTRODUCTION ................................................................................. 4 GENERAL ANALYTICAL CLINICAL LABORATORY DIAGNOSTICS ..................................................................................... 6 LABORATORY ASSESSMENT OF RENAL FUNCTION ............. 14 CLINICAL HEMATOLOGY ............................................................. 47 LABORATORY ASSESSMENT OF HEMOSTASIS ....................... 76 CLINICAL METHODS OF EXAMINATION .................................. 84 REFERENCES .................................................................................... 99 3 INTRODUCTION Diversity of nosologycal forms, peculiarities of their manifestations in different patients makes diagnosing difficult; subjective means depending on doctor's skills and knowledge are not enough. Clinical medicine constantly seeks modern objective footholds in scientific achievements of biology, physics, chemistry, technology and electronics. As a result the sphere of laboratory diagnostics in modern evidentiary medicine is steadily widening. Major responsibility for quality of diagnostics and treatment is layed on a clinician, but adequate laboratory-diagnostic service makes his job considerably easier. Laboratory studies a number of biological material samples of a patient and detects diagnostically significant characteristics: 1) Qualitative (structural) – form and structure of the cells, presence of chemical compounds of specific structure (for example, hemoglobin variants, enzymes in urine, etc.); 2) Quantitative – size and correlation of structural components; chemical compounds concentration; number of certain cellular elements; balance of structurally close elements (for example, albumin-globulin coefficient); 3) Functional – realization of transformation cycle (glucose tolerance test) and circulation of substances in an organism, development cycle, cell maturation. The main function of clinical diagnostic laboratory is to present authentic information on composition of biological materials samples, taken from a patient and on a degree of correspondence of this composition indices to a generally accepted ―norm‖. Resources of laboratory diagnostics include early (preclinical) pathology verification, confirmation and differential diagnostics of clinically manifested nosological forms as well as therapy efficiency evaluation. Clinical laboratory diagnostics includes study of organic and non- organic chemical substances and biochemical processes in blood and other human‘s biofluids in order to diagnose, monitor a disease course, detect prognosis and screen a disease. 4 Clinical laboratory diagnostics is a discipline on clinical diagnostics which deals with the development and use of standard diagnostic and disease control methods. Clinical laboratory diagnostics allows to make scientifically based diagnosing easier, it helps to chose the methods of adequate treatment and disease prevention. Clinical laboratory diagnostics includes such parts as clinical biochemistry, clinical laboratory hematology, immunology, clinical serology and microbiology, clinical toxicology and others. It disposes a wide range of diagnostic tests, information and development prospective, which enables a clinicist to solve the questions of pathogenesis and etiology of a pathological process. Information received due to laboratory research methods allows to asses dynamics of pathological process development at molecular, cellular and organ levels, which is essential for modern disease diagnostics and for evaluation of therapy efficiency. Clinical laboratory diagnostics is mostly based on theoretical basis and is closely connected with such sciences as general and bioorganic chemistry, biologic chemistry, histology, normal and pathologic physiology and pathologic anatomy. 5 GENERAL ANALYTICAL CLINICAL LABORATORY DIAGNOSTICS Stages of laboratory examination A patient‘s laboratory examination is usually divided into three stages: pre-analytic, analytic and post-analytic. Analytic stage takes place in laboratory; the other two stages require significant extra laboratory work. It is important to understand that, as in any sphere of human activity, it is impossible to avoid some mistakes in clinical diagnostic laboratories. The aim of each laboratory is, using quality control system, to develop reliable set of tools, which allows to detect the mistakes and to make arrangements in order to minimize these mistakes. Quality assurance is a complex of planned and systematically performed activities, necessary to be confident that diagnostic information in the authorized report corresponds to certain quality requirements. Undoubtedly, it is a patient who is interested in high quality of laboratory attendance. Specialists in clinical laboratory diagnostics are interested in quality of their product as well. As any professional, they need to be confident that their work is well done. Quality of work as motivation is one of the components of professionalism. Another group of concerned persons are clinicians as main users of diagnostic information, including laboratory examination data. Part of laboratory indices in the whole flow of diagnostic information, used by a clinician comprises 70-80%. The question of laboratory tests standardization in general, and at this stage particularly, is rather acute. Laboratory examination starts with appointment of tests list, necessary for diagnosing and observing a patient's condition. One of the widespread reasons of mistakes is inadequate laboratory examination. A valuable test will have no use if the analysis results are not used. There are following reasons of inadequate laboratory tests appointment: diagnostic test value variability of reference values 6 use of negative results and assessment of tests complex (comparison of tests results) disease course doubling of laboratory tests sufficiency of diagnostic information. A doctor should understand that laboratory tests, appointed to approve or eliminate the diagnosis, can be more harmful than useful. It is evident, that there is no a unified standard on pre-analytic stage performance and hardly it will ever appear (due to broad specificity of medical institutions and clinical diagnostic laboratories). There are differences in work organization of centralized laboratory and hospital laboratory. In this case each medical institution needs to develop and approve the standard of this stage of laboratory examination performance taking into consideration recognized international and national standards and recommendations. Preparing the patient for laboratory tests is one of the most important components of pre-analytical stage. Certain actions should be obligatory performed: a clinician should explain the necessity of laboratory examination to a patient a nurse should inform a patient on how to get prepared for examination/ Laboratory part of pre-analytical stage starts from the moment of sample delivery and application to laboratory. This part has following steps: organization of test performance and applications (registration of patient's tests); samples identification, centrifugation; conditions and terms of samples preservation if necessary; detection of influences (hemolysis, lipemia) and admixtures (drugs metabolites, impurity); distribution of samples to laboratory departments (laboratory assistants), examination performance. In the laboratory it is recommended to arrange the place where biological material will be collected. On receiving the material a receptionist checks correspondence of samples to applications, samples state, date of sampling and delivering the material. Specialists 7 in clinical laboratory diagnostics should determine and confirm criteria for refusal in material examination (for example, divergence of data in application and on a tube label, impossibility to read an application, the material was taken with the wrong anticoagulant or preservative, expiring of delivery terms, clots in whole blood with coagulant, etc.). After centrifugation the most common refusal criteria are: hemolysis, sample turbidity. Various kinds of material are centrifugated and then used for laboratory tests. Assessment of centrifugation time is, first of all, a certain correspondence of time and conditions of centrifugation to this or that kind of material (visual centrifugation control). The basic control form of pre-analytic stage is periodic internal and external checkups. But this control form can not be considered an effective one. The problem of control over that laboratory examination stage remains one of the major problems of modern laboratory medicine today. In modern clinics and clinical diagnostic laboratories about 90- 95% of blood and other biological samples are collected by vacuum systems. Comparison of costs of open blood sampling (syringe blood sampling), secondary tubes for analyzers, syringes, needles, detergents, disinfectants, electricity, additional equipment for cleaning test tubes, glass breakage accounting, purchasing the necessary reagents (anticoagulants: EDTA, citrate, heparin ) and wages for the personnel on the one hand, and the acquisition of advanced systems for the collection of biological material (blood, urine), on the other hand, shows that the economic costs are comparable. But we can not ignore the factor of a significant risk reduction of personnel contamination with hepatitis and HIV when using blood collection systems (while blood sampling the sterility is guaranteed, the contact with the blood of a patient is excluded, so medical personnel and patients are safe as well as transportation of biological material). Without the introduction of vacuum or other systems for blood and body fluids collection into general practice we can‘t expect the improvement of the pre-analytic stage and quality of laboratory examination. 8 Biological material, used in laboratory examinations The most widespread materials for clinical biological examination are blood, urine and some other biological fluids. The blood is recommended to be collected in the morning (between 8 and 10 a.m.) before physical activity and other diagnostic procedures. On a day before blood sampling meals can be normal, but alcohol should be excluded. Healthy and ambulatory patients are forbidden to smoke (after 2 a.m.), eat and drink (a glass of water is allowed at 10 p.m. – 5 a.m.) Most blood tests require 8-12 hours‘ fasting, but to detect triacylglycerols there should be a 10-12-hour interval after a meal. Just prior to blood sampling a patient should take a sit for 10-30 minutes (the procedure is performed with the hand placed at an angle of 45 degrees). The blood in patients with a strict bed rest should be collected at 7-9 a.m., and a patient‘s hand should be placed horizontally. It should be noted that when people stay in a horizontal position for a few hours plasma volume in blood is 10-15% higher than that of a patient with normal motor activity. So the concentration of substances in the blood of a patient lying more than an hour is always lower than of a patient after a walk. Body position influences the concentration of whole protein, albumin, creatinine, cholesterol, triacylglycerol, alkaline phosphatase activity, aspartate aminotransferase and other plasma components. Content of these substances and enzyme activity are considerably increased in an upright patient‘s position and decreased in a horizontal position. The maximum change is characteristic of the total protein level, enzyme activity (11%) and calcium content (3-4%). When collecting the blood by venipuncture the time of vascular embarrassment with tourniquet should be minimal. A patient shouldn‘t bend and straighten the finger as it induces local stasis, hypoxia and shifts in distribution of some substances (cholesterol, potassium, sodium, calcium etc.) between blood corpuscles and its fluid part. If it is impossible to use a single- use syringe one should boil a reusable syringe in distilled water only, and it shouldn‘t be washed by isotonic sodium chloride solution. To avoid hemolysis blood should be collected by a dry syringe, dry needle, into a dry test tube under sterile conditions. If the blood is transferred from a syringe to a test tube this procedure should be performed slowly (to avoid blood foaming). In hemostasis system 9 examination there is a number of additional requirements for blood sampling. So, it is recommended to use a wide lumen needle without a syringe (it is used for blood collecting in children, adults with hypotension or in terminal states; a syringe should be plastic or siliconized). Skin disinfection (skin area above the puncture site in the bend of elbow) should be performed by 70% ethyl alcohol. As a needle passes through the skin tissue fluid and tissue fragments can be found in a needle lumen. These substances can significantly affect coagulation tests, so the first (after a tourniquet application and vein puncture) 0,5-1,0 ml of blood should not be used for coagulogram. But this blood portion can be used for all the other biochemical tests. To exclude the influence of passive venous congestion on coagulation, it is recommended to loose a tourniquet for 2-3 seconds while venous blood collection. The blood should flow down the walls of a tube. If it is necessary to receive plasma the corresponding coagulant (lithium citrate, sodium or potassium oxalate, etc.) should be put into a test tube beforehand to avoid blood from clotting. The blood is carefully mixed with anticoagulant (without foaming), a test tube is covered with a piece of polyfilm and left on a rack for 20-25 min. Intensive shaking causes erythrocytes hemolysis, which distorts the parameters of coagulogram.That is why plasma with hemolysis signs is not suitable for such kind of examination. Table 1. Types of biological materials, examined in clinical diagnostic laboratories Is collected from the major veins (usually from the Venous whole ulnar vein) into a test tube, containing blood anticoagulants (EDTA) for hematologic tests. Is collected from the major arteries (usually Arterial whole femoral or subclavicular) into a test tube, blood containing anticoagulant. Arterial blood collection requires special care and should be performed by a doctor. Most often heparin is used as anticoagulant in that case. Usually arterial blood is used for acid- base balance analysis. 10