Fundamentals of clinical epidemiology. Clinical epidemiology

For independent extracurricular work

to practical lesson No. 2

in the discipline Evidence-based medicine

specialty (direction of training)

"Medicine"

Compiled by: cand. honey. Sciences Babenko L.G.

Theme II. Clinical epidemiology is the basis of evidence-based medicine

Purpose of the lesson: study of goals, objectives, principles and methodology of evidence-based medicine; criteria and degree of evidence for studies of etiology, diagnosis, treatment and prognosis and the scope of their application; historical aspects of its formation and development.

Tasks:

1. To acquaint students with the sections of evidence-based medicine, its goals, objectives, principles, components, aspects and methodology, its place among other medical sciences.

2. Describe the degree of evidence in clinical studies of etiology, diagnosis, treatment and prognosis and the scope of its application.

3. Highlight the historical aspects of the creation, formation and development of evidence-based medicine

4. Familiarize students with the organization that professes the methodology of evidence-based medicine Cochrane Collaboration, its goals, objectives and principles.

5. Describe the difficulties of introducing evidence-based medical practice and ways to overcome them in domestic medicine.

The student must know:

1 - before studying the topic (basic knowledge):

The main factors, trends in the development of biomedical sciences and the needs of practical medicine in modern conditions;

Components of building a medical view on methodological approaches to conducting clinical trials, evaluating and applying their results;

Mathematical methods for solving intellectual problems and their application in medicine;

Fundamentals of Medical History;

Theoretical foundations of informatics, collection, storage, search, processing, transformation of information in medical and biological systems, the use of information computer systems in medicine and healthcare;

The concepts of etiology, pathogenesis, morphogenesis, pathomorphosis of the disease, nosology, the basic concepts of general nosology:

Functional bases of diseases and pathological processes, causes, main mechanisms of development and outcomes of typical pathological processes, dysfunctions of organs and systems.

2 - after studying the topic:

Basic concepts, purpose, objectives, principles and methodology of evidence-based medicine;

Degrees of evidence in clinical studies of etiology, diagnosis, treatment and prognosis and the scope of its practical application;

The main historical stages of the formation and development of evidence-based medicine;

The significance of the Cochrane Collaboration for clinical medicine and the forms of its activities abroad and in Russia;

Difficulties in implementing evidence-based medical practice and ways to overcome them

The student must be able to:

- competently and independently analyze and evaluate and analyze the clinical features of the manifestation of the patient's pathology and carry out their activities taking into account the principles and methodology of evidence-based medicine;

Use the information resources of the Cochrane Library to make clinical decisions based on the principles of evidence and reliability in order to obtain a high-quality and effective clinical outcome.

The student must be proficient in:

Terms and concepts clinical epidemiology;

Measuring total error in a clinical trial;

Assessment of health levels in medical and social studies;

Methods for calculating indices and indicators of health;

Formation of a cohort for scientific and clinical research;

Formation of a population for scientific and clinical research.

Tasks for independent extracurricular work of students on the specified topic:

1 - get acquainted with the theoretical material on the topic of the lesson using lecture notes and / or recommended educational literature and sources;

2 - to state in writing in the workbook "Glossary" the essence of the terms and concepts used on this topic of the seminar:

The health and well-being of the nation

Formation of a healthy lifestyle

1. Creation of conditions and development of health factors, motivation to be healthy:

Physical and mental comfort

High labor activity with job satisfaction

Active life position, social optimism, high culture, great energy potential

environmental literacy

Rational nutrition and physical culture

good family

2. Overcoming risk factors:

Physical inactivity, smoking, alcohol abuse, excessive malnutrition

Unhealthy family life

Bad job positions

It is necessary to give human health the status of the main social value, a factor of national security and the main criterion for the effectiveness of society management.

Legislatively fix the complex concept of “protecting the health of the nation”.

The “Concept for the Development of Public Health and Medical Science in the Russian Federation” was adopted in November 1997. It includes the main provisions for the protection and promotion of the health of the nation. At the same time, there is no law on health care, no strategic development program. The emphasis is on individual areas and programs in health care reform:

Development of a public health promotion policy.

Creating an enabling environment

Strengthening social activity.

Development of personal skills and knowledge.

Reorientation of health services towards prevention.

Methods for studying OZ and OZ:

The methodological base is at the intersection of knowledge from sociology, statistics, epidemiology, economics, computer science, social psychology and other medical sciences

historical method

expert method

sociological methods

System analysis

Method of organizational experiment

Economic methods (normative, planning..)

Integrated method of socio-hygienic research

Methods of clinical epidemiology and evidence-based medicine

The health of the population depends on a complex of factors:

There are factorial signs, that is, causes

Efficient signs, that is, consequences.

A factor is the cause of any phenomenon that determines its nature (there are natural-climatic, social, medical, and other factors).

There are 4 types of medical and social research:

One factor - one result;

Complex of factors - one result;

One factor-complex results;

A complex of factors is a complex of results.

Epidemiology is the science of the causes and patterns of occurrence and development of pathological processes, diseases in society, using epidemiological research methods to develop measures for the prevention and optimal treatment of diseases.

Clinical epidemiology is a science that allows prediction for each individual patient, based on the study of the clinical course of the disease in similar cases, using rigorous scientific methods of studying groups of patients to ensure accurate predictions. .

Metric requirements:

Data Availability

Completeness of coverage

Quality

Versatility

Computability

Reproducibility

Specificity

Sensitivity

Validity

Representativeness

Hierarchy

Target solvency

Research stages:

1. Preparatory organizational stage.

2. The stage of collecting information and forming databases.

3. The stage of data processing, analysis and visualization, literary and graphical display.

Stage 1 - study design development:

1. Program development includes:

Purpose of the study

Research objectives

Formulation of the topic, clarification of the terms used, glossary of concepts.

Formulation of hypotheses.

Definition of the object and unit of observation. The object of study is a statistical set consisting of homogeneous units taken together within known boundaries of time and space. The unit of observation is the primary element of the statistical population.

Development of statistical tools (questionnaires, maps, information programs)

2. Formation of a work plan:

The procedure for the selection, training and organization of the work of performers.

Determination of the required volume, resources for study.

Definition of responsible executors, terms.

Formation of the working grid-schedule of the study.

Methods for selecting observation units:

1. Continuous (the entire general population) and non-continuous study.

Monographic study (deep study of one unit: person, institution)

Main array method (most of the object is studied)

Sampling method - selection of a representative sample that meets all the requirements of the total sample (methods of formation - random, mechanical, typological, serial)

Method of multi-stage selection (stage 1 - all employees, stage 2 - women Formation methods can be different at the stages, random, typological)

Directed selection method (Experience, age)

Cohort method (set in one place at one time.)

Copy-Pair Method for Studying Rare Phenomena

Methods for collecting statistical information

The research program includes:

Description of health conditions

Description of conditions and lifestyle

Information can be obtained from 3 main sources:

1. Official statistics data
2. Copying data from primary documentation
3. Direct research

Ways to get information

Questionnaire

Interviewing (face-to-face survey)

Questionnaire-interview

Observation Method

Expeditionary monographic

budget

The questionnaire contains: introductory (the purpose of the survey), the main, socio-demographic part.

Questionnaire requirements (formulate meaningful questions that are understandable to the respondent; there should be no questions that cause unwillingness to answer; the sequence of questions in achieving the goal)

Open question does not provide clues

A closed question contains multiple choice answers (alternative question: yes; no; multiple choice question).

semi-closed question

direct question

Indirect question

Security Question for Validation

Questions filters (to separate respondents into knowledgeable and ignorant)

Table Layout Methodology

The table must have a clear title

Tables must have the same numbering

Registration ends with a total of columns and lines

Subject in the table (the main feature, usually located horizontally)

The predicate, the sign that characterizes the subject is more often located in columns

Simple table.

Group table (the subject has several unrelated predicates.

Combined, predicates are interconnected.

Stage 2 - collecting information and forming databases:

Data is information presented in a formalized form.

To collect, store and process data, programs called databases are used.

Data array - resides in the database and is managed by database management systems

Requirement - the possibility of developing and improving the system for collecting and storing information

Stage 3 - processing, analysis, literary and graphic design:

Data processing is the process of obtaining reliable, previously unknown information and using it for analysis and management decision making.

Data processing steps:

Data preparation

A priori exploratory analysis

Choice of analysis method

Interpretation and presentation of results

Preliminary preparation-grouping of data. The distribution of the statistical population into homogeneous groups according to one or more characteristics (sex, age, profession). Simple and combined grouping. secondary grouping. Definition of the age interval.

A priori analysis:

1. Identification of reasonable causal relationships.
2. Assessment of the homogeneity of the studied population (determination of anomalous phenomena, selection of the optimal allocation of homogeneous groups)
3. Analysis of the nature of the distribution of the population by characteristics
4. Each chart must have a clear title.
5. All elements must be explained
6. The depicted graphic values ​​must have numerical designations on the diagram or attached table.
7. Distinguish: cartogram diagrams cartograms.
8. The line chart shows the dynamics of development
9. Bar charts are used for discrete quantities
10. strip chart
11. Pie chart usually to reflect the structure in%.

– Disclosure of results to the public

– Development of comprehensive medical and social programs

– Preparation of draft orders, methodological recommendations at different levels (institutions, district)

– Preparation of draft laws, executive and legislative resolutions

– Reorganization of the network of medical institutions and the healthcare system

– Publication in print, registration of inventions, discoveries

The main types and tasks of professional activity in the field of healthcare organization and public health:

1. Analysis of the health status of the population:

Organize registration and collection of information on the state of health of the population and its individual groups;

Own methods of analysis and evaluation of the received information about public health;

Conduct an analysis of the health status of the individual, family, population and its individual groups;

Identify, analyze and evaluate health indicators of the population and its individual groups based on epidemiological information;

Establish the factors that determine the health of the individual, family, population and its individual groups;

Analyze socio-economic factors affecting the health of the population;

Take into account lifestyle factors, biological, genetic and environmental factors affecting the health of the population;

Determine factors and indicators of risk and health factors (anti-risk);

Predict changes in public health indicators;

Take into account the peculiarities of the drug supply system that affect the health of the population (production, distribution, pharmacies, falsification).

2. Analysis of the activities of health authorities and health organization:

Organize accounting and collection of information on the results of the activities of healthcare organizations, individual teams;

Own methods of analysis and evaluation of the information received;

Analyze the performance of healthcare organizations, production units, individual employees;

Conduct a situational analysis of the health care system and its individual sectors (subsystems);

Analyze the market of medical services (pharmaceutical, preventive);

Evaluate the results of a preventive intervention program;

Analyze the turnover of material resources, the efficiency of their use;

Analyze accounting information and financial statements;

Analyze the characteristics of management, accounting and auditing to make the best decisions.

Clinical epidemiology (Clinical epidemiology) is a science that allows prediction for each individual patient based on the study of the clinical course of the disease in similar cases, using rigorous scientific methods of studying groups of patients to ensure accurate predictions.

The goal of clinical epidemiology is to develop and apply methods of clinical observation that make it possible to draw fair conclusions, avoiding the influence of systematic and random errors. This is the most important approach to obtaining the information doctors need to make the right decisions.

A systematic error, or bias (bias) is "a systematic (non-random, unidirectional) deviation of the results from the true values"

Bias Assume that drug A was found to work better than drug B. What kind of bias could lead to this conclusion if it turned out to be wrong? Drug A could be given to patients with lesser disease severity; then the results will be due not to the different effectiveness of drugs, but to the systematic difference in the condition of patients in the two groups. Or drug A tastes better than drug B, so patients adhere to the treatment regimen more strictly. Or drug A is a new, very popular drug, and B is an old drug, so researchers and patients tend to think that a new drug will definitely work better. These are examples of possible systematic errors.

In most cases, the prognosis, diagnosis and treatment outcomes for a particular patient are not unequivocally certain and therefore they must be expressed in terms of probability; - these probabilities for a particular patient are best estimated on the basis of previous experience accumulated by doctors with groups of similar patients; - since clinical observations are carried out on patients who are free in their behavior and by doctors with different levels of knowledge and their own opinions, the results do not exclude systematic errors that lead to biased conclusions; - any observations, including clinical ones, are influenced by chance; To avoid incorrect conclusions, the physician must rely on studies that are based on rigorous scientific principles using methods to minimize systematic errors and account for random errors. Fundamentals of Clinical Epidemiology

Clinical questions Diagnosis How accurate are diagnostic methods for the disease Frequency How common is the disease? Risk What factors are associated with increased risk? prognosis What are the consequences of the disease? TreatmentHow will the disease change with treatment? Prevention What are the methods of prof. And its effectiveness Causes What are the causes of the disease Cost How much does the treatment cost Discussion question Deviation from the norm Healthy or sick?

Clinical outcomes Death (Death) Poor outcome if death is premature Disease Abnormal set of symptoms, physical and laboratory findings Discomfort Symptoms such as pain, nausea, shortness of breath, itching, tinnitus Disability Inability to carry out normal activities at home, at work, during leisure Dissatisfaction Emotional reaction to illness and treatment, such as sadness or anger

The study and use of clinical epidemiology requires additional effort and time from a doctor who is sufficiently engaged in practical work. And he needs this: - Firstly, the doctor constantly receives intellectual pleasure and a sense of confidence, often instead of surprise and disappointment. -Secondly, the effectiveness of the perception of medical information is growing significantly, because now the doctor can, based on fundamental principles, quickly figure out which sources of information are trustworthy and can be used to improve the effectiveness and safety of treatment.

Thirdly, thanks to the principles of clinical epidemiology, physicians of any field of medicine receive the only scientific base, because they rely primarily on well-organized and reliable results of clinical trials. Fourth, clinical epidemiology allows the clinician to judge the extent to which his efforts to combat other factors - biological, physical, social, can positively affect the results of treatment. In other words, the doctor becomes convinced of what he is able to do and what he cannot do.

Clinical epidemiology and diagnostic tests Pre-test probability of the presence of a disease Sensitivity and specificity of a diagnostic test Predictive value of a diagnostic test Population with a low probability of disease Lecture abstracts: Principles of evidence-based medicine a relatively short period of time, the main ...

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F KSMU 4/3-04/01

IP No. 6 UMS at KazGMA

KARAGANDA STATE MEDICAL UNIVERSITY

Department of Epidemiology and Communal Hygiene

LECTURE

Topic: "Basic provisions and principles of clinical epidemiology, the relationship of clinical epidemiology with biostatistics."

Subject: BDO 26 Epid - 3226 Epidemiology

Specialty: 051301 - " General Medicine »

Course 3

Time (duration) 1 hour

Karaganda 2010

Approved at the meeting of the department

"____" ____________ 2010 Protocol No. ___

Head Department of Epidemiology and

of Communal Hygiene Doctor of Medical Sciences, Professor __________ Shabdarbayeva M.S.

Subject: "Basic provisions and principles of clinical epidemiology, the relationship of clinical epidemiology with biostatistics".

Purpose: mastering the scientific and organizational foundations of clinical epidemiology.

• Lecture plan:

• Lecture abstracts:

1. Principles of evidence-based medicine

The term "evidence-based medicine" or "evidence-based medicine" ( evidence based medicine ) appeared in the lexicon of modern medical specialists quite recently, however, in a relatively short period of time, the basic principles invested in the meaning of this term constituted the dominant ideology of medicine. XXI century. With the help of “evidence”, it became possible, if not to make medicine an exact science, then at least to bring it closer to one.

This term was proposed in 1990 by a group of Canadian scientists from McMaster University in Toronto.

The definition formulated by the Evidence-Based Medicine Working Group, with some of our additions, is as follows:

"Evidence-based medicine is a branch of medicine based on evidence, involving the search, comparison and wide dissemination of the obtained evidence for use in the interests of patients (clinical epidemiology) or in the interests of the whole population (preventive evidence-based medicine)."

Recently, there are various options for defining the concept of "evidence-based medicine" (EBM):

• DM is a benign, accurate and meaningful use of the best results of clinical trials to select the treatment of a particular patient (clinical epidemiology);
• DM is a method (variant) of medical practice, when a doctor uses only those methods in the management of a patient, the usefulness of which has been proven in benign studies (clinical epidemiology);
• DM is an approach to health care that collects, interprets, and integrates reliable, important, and practical evidence from special studies that take into account clinician observations and patient complaints (clinical epidemiology), as well as the health status of the population (public health) ;
• DM is a new approach to technologies for collecting, summarizing and interpreting
  medical information.

The essence of the above definitions is to optimize the quality of medical services to the population (a specific patient) in terms of their safety, benefits, efficiency, acceptable cost, etc. -2010" and the strategic direction of the activities of the Ministry of Health of the Republic of Kazakhstan to control the quality of medical and pharmaceutical care for the population.

Evidence-based medicine is based on "clinical epidemiology", which is a branch of medicine that uses epidemiological methods to obtain medical information based only on strictly proven scientific facts, excluding the influence of systematic and random errors.

Term clinical epidemiology(CE) comes from the name of two "parent" disciplines: "clinical medicine" and "epidemiology". It is necessary to clearly distinguish between the purpose and purpose of these two disciplines and the tasks of clinical epidemiology:

• "clinical epidemiology" ( clinical epidemiology ) is a "clinical" science because it seeks to answer clinical questions and recommend clinical decisions based on the most reliable evidence. In other words, "clinical epidemiology" is a science that develops clinical research methods that make it possible to draw comprehensively sound conclusions, controlling the influence of systematic and random errors;
• from an epidemiological point of view, this is a branch of medicine that uses epidemiological methods to obtain medical information based only on strictly proven scientific facts that are not affected by systematic and random errors. Consequently, epidemiology is a field of science, where its various directions (identification of “risk” factors or a causal factor, or a module of causality, behind which a “consequence” is opened in the form of a disease and the doctor’s response measures - ways to eliminate them) are carried out by an epidemiologist in a wide range of real facts . Here, specific assistance to the patient is considered in the context of a large population of the population (a group of people at risk of disease (infection), to which a specific individual (sick person) belongs);
• a close relationship between the epidemiologist and the clinician is necessary, without which their actions are limited, uncoordinated and ineffective in addressing the issue of protecting the health of a particular person and the population as a whole.

The main postulate of clinical epidemiology isany decision in medical practice must be based on rigorously proven facts,which are the basis for evidence-based medicine.

Being part of medicine, epidemiology as a science differs from clinical medical practice in its approach to the problem: the epidemiologist studies the differences and common features of diseases in order to help large groups of people (populations, populations). Actually, the “epidemiological diagnosis” differs from the “clinical diagnosis”. In the first case, the causes, conditions and mechanisms of the formation of the incidence of the population are determined by analyzing its distribution across territories, among various groups and collectives, as well as over time and among subjects with different characteristics. At the same time, diseases are separated as a phenomenon observed in an individual organism (clinical epidemiology) and morbidity (a set of cases in a population). In the case of a "clinical diagnosis", the disease is considered in a specific individual. It should be noted that only the elimination of "risk factors" for the occurrence of a disease of an infectious or somatic nature (morbidity of the population) can solve the main issue - the preservation and improvement of the health of the population. Therefore, epidemiology is considered to be the foundation of public health science.

In a narrow sense, the task of evidence-based medicine is to transform the results of scientific research into concrete clinical and preventive solutions and recommendations for physicians.

An important aspect of evidence-based medicine has become the establishment of the degree of reliability and significance, i.e. "evidence" of medical information.

According to the Swedish Council for Health Evaluation Methodology, the reliability of evidence from different sources is not uniform and depends on the type of study conducted. Confidence decreases in this order:

• randomized controlled clinical trial;
• non-randomized clinical trial with simultaneous control;
• non-randomized clinical trial with historical control;
• cohort study;
• "case-control";
• cross clinical trial;
• observation results.

Meta-analysis

Randomized (extreme) controlled trials (the "gold standard")

Analytical studies (cohort, "case control")

Descriptive studies

Expert opinion

The assessment of the reliability (evidence) of the information received implies the answer to three main questions:

• Are the results of the studies justified (validity)?
• What are these results (reliability/validity)?
• Will the on-site results help (applicability)?

The Center for Evidence-Based Medicine at Oxford offers the following criteria for the reliability of medical information:

High Confidence- information is based on the results of several independent clinical trials with agreement between the results summarized in systematic reviews.

Moderate certainty- the information is based on the results of at least several independent, similar clinical trials.

Limited certainty- the information is based on the results of one clinical trial.

There is no rigorous scientific evidence(clinical trials not conducted) - a certain statement is based on the opinion of experts.

Applied to laboratory diagnosticsevidence must be provided at several levels:

• at the technical (or technological) levelit is necessary to prove that the information obtained reliably reflects the state of the function of an organ or tissue of interest to the researcher;
• at the diagnostic levelit must be shown that the analysis being performed is in a proven causal relationship with the suspected pathology and the correspondinglaboratory testhas a certaindiagnostic specificity(number of negative responses in the healthy group) andsensitivity(number of positive test responses in a group of patients with a given disease).

For a comprehensive assessment of the test in terms of its sensitivity and specificity, graphs of characteristic curves are used.

At its core, evidence-based medicine is a new approach to the technology of collecting, analyzing, summarizing and interpreting facts and information for the processes of diagnosis, treatment and prevention, the purpose of which is to provide evidence-based criteria and principles for planning, conducting, analyzing clinical, diagnostic, epidemiological studies and application their results in everyday practical medical activity, calledevidence-based medical practice.

1. Clinical epidemiology and diagnostic tests

The materials of the Oxford Center for Evidence-Based Medicine include the following aspects:

• pre-test probability of having a disease;
• sensitivity and specificity of the Diagnostic study
  (indicators of sensitivity and specificity of some diagnostic
  ical tests);
• predictive value of a diagnostic test.
  

Pre-test probability of having a disease

Project assessments of situations prior to receiving the results of a diagnostic test. Pre-test probability is especially useful in four cases:

1. When interpreting the results of a diagnostic study.
2. When selecting one or more diagnostic studies.
3. When choosing whether to start therapy:

A) without further investigation (treatment threshold);

B) while waiting for further research.

1. When deciding whether to conduct a study at all (testing threshold).

Sensitivity and specificity of the diagnostic test

Any clinical test(lab test, objective test) is not perfect. There is always the possibility that test results do not reflect the objective presence or absence of a disease.

The presence (or absence) of pathology is established by a certain reference, standard method, otherwise called the “gold standard of diagnosis”. It is clear that the reference method is also not 100% accurate. As a rule, the use of the reference diagnostic method is limited by a number of inconveniences - from a high risk of complications to high cost.

To judge how good a given diagnostic test isrelative to the standardthe concepts of sensitivity and specificity of a diagnostic test are proposed.

Sensitivity ( sensitiviny ): the proportion of people with a disease who have a positive diagnostic test.

specificity ): the proportion of people without disease who have a negative diagnostic test.

To illustrate the relationship between the results of a clinical test and an objectively existing (or non-existing) pathology, the so-calledquadruple table.

Sensitivity ( Se) \u003d a / (a ​​+ c)

Specificity (S p) = d /(b+ d )

Sensitive Testoften gives a positive result in the presence of the disease (detects it). However, it is especially informative when it gives a negative result, because. rarely misses sick patients.

specific testrarely gives a positive result in the absence of disease. It is especially informative with a positive result, confirming the (presumed) diagnosis.

There are two rules that greatly aid in the use of sensitivity and specificity data for a diagnostic test:

• 1 rule reminding that a highly sensitive sign, test or symptom, if negative, excludes the disease;
• 2 rule reminding that a highly specific sign, test or symptom, if positive, confirms the disease.

The predictive value of a diagnostic test

The predictive value of the test is the probability of the presence (absence) of the disease with a known result of the study.

As disease prevalence approaches 0%, the positive predictive value approaches zero.

As the prevalence approaches 100%, the negative predictive value tends to zero.

After conducting a clinical test (not necessarily a laboratory one), it is necessary to answer the main question - is the subject sick. This is where the concept of the predictive value of a test comes in handy.

The predictive value of a positive result is the probability of having a disease in a positive (abnormal) test result.

The predictive value of a negative result is the probability of the absence of disease in a negative (normal) test result.

Factors that determine the predictive value of a test

The predictive value depends on:

• sensitivity and specificity of the diagnostic method;
• the prevalence of the disease in the study population.

Prevalence (p revalen ce) is defined as the ratio of the number of individuals with a disease (or any other condition) to the entire study population. The prevalence is called a priori (pretest) probability, i.e. is the probability of detecting a disease before the test results are known. The predictive value is called the posterior (post-test) probability of the disease.

The formula that relates the sensitivity, specificity, and prevalence of a disease to the positive predictive value is derived from Bayes' theorem.

where

R V - Positive predictive value

S e - Sensitivity

P - Prevalence

(according to R. Fletcher et al. Clinical epidemiology. Fundamentals of evidence-based medicine, M., 2004)

The more sensitive the negative result (i.e., it increases the likelihood that negative test results reject the presence of the disease). On the contrary, than more specific test, the higher its predictive value positive result (i.e., the likelihood that a positive test result confirms a suspected diagnosis increases).

Interpretation of predictive value

The interpretation of the predictive value of a positive or negative test result varies with the prevalence of the disease.

Population with a low probability of disease

If positive results of even a highly specific test are obtained in a population withlow probabilitydiseases, they will be predominantlyfalse positive.

In a population without the disease being studied, all positive results will be false positives, so as the prevalence of the disease goes to zero, the positive predictive value goes to zero.

Population with a high probability of disease

Negative results from a highly sensitive test obtained in a population with a high probability of having the disease are more likely to be false negatives.

In a population where everyone has the disease, all negative results, even on a highly sensitive test, will be false negatives. As prevalence approaches 100%, the negative predictive value approaches zero.

• Illustrated material (tables, slides).

1. Research Evidence Pyramid
2. Construction of a four-field table.

• Literature:
• Vlasov V.V. Epidemiology. Tutorial. 2nd edition - M., 2006
• Pokrovsky V.I., Briko N.I. Guide to practical exercises in general epidemiology with the basics of evidence-based medicine. Textbook - M., 2008.
• Yushchuk N.D., Martynov Yu.V. Epidemiology. - M.: Medicine, 2003.
• Amireev S.A. Epidemiology. 2 vol. Almaty 2002.

• Control questions (feedback):

1. Principles of evidence-based medicine.
2. Clinical epidemiology and diagnostic tests.
3. Pre-test probability of having a disease.
4. Sensitivity and specificity of the diagnostic test.
5. The predictive value of a diagnostic test.
6. Population with a low probability of disease.

CLINICAL EPIDEMIOLOGY

BASICS OF EVIDENCE-BASED MEDICINE

Professor Mamatkulov B.M.., Director of the School of Public Health, TMA;

Professor LaMort, Boston University, School of Public Health (USA);

Assistant Rakhmanova Nilufar, SHZ Assistant, TMA, USAID

Reviewers:

Peter Campbell, Regional Quality Improvement Director

USAID Zdrav Plus Project

A.S. Bobozhanov, professor, head of the department of public health, organization and management of health care

L.Yu.Kuptsova, Associate Professor of the Department of Health Organization, Economics and Health Management, TashIUV

TASHKENT - 2013

Foreword

Clinical epidemiology is the medical subject that studies the spread of disease, its determinants, and frequency of occurrence in the human population. This subject underlies the subject of Evidence-Based Medicine, which is currently widely promoted in our country and abroad as a tool for making evidence-based clinical decisions. Clinical epidemiology as the main special discipline is studied at the faculties of public health.

To date, no training package has been prepared that includes a list of presentations, handouts and teaching aids necessary for the full teaching of this subject.

At present, the theoretical and practical foundations of Clinical Epidemiology, a modern field that is becoming increasingly necessary in the healthcare system of Uzbekistan, are not sufficiently implemented in the medical education system. One of the reasons for this situation is that there is not enough literature on this subject. The available literature is in English and therefore not accessible to both students and teachers.

In this regard, this manual "clinical epidemiology" is a necessary tool for teaching masters of medical universities and the School of Public Health, Tashkent Medical Academy. The textbook is designed to meet the needs of masters, and each chapter includes the knowledge and skills that the resident must acquire. The manual can also be useful for graduate students, residents, physicians and healthcare organizers.

The book is devoted, first of all, to the assessment of the quality of clinical information and its correct interpretation. Decision making is a different matter. Of course, the right decision requires reliable information; however, they need something much more, in particular, the determination of the price of the decision, the comparison of risk and benefit.

RANDOMIZED CONTROL STUDY EVALUATION TABLE 442

GLOSSARY OF TERMS 444

LITERATURE 452

Separate Chapter of the Foundation of Evidence-Based Medicine