Clinical epidemiology: definition, development history, main principles and research methods
The epidemiological technique as the set of methods intended for studying of the reasons, conditions of occurrence and distribution of illnesses and other conditions in population of people. Clinical epidemiology and social aspects of medical aid.
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Has historically developed so that in the XX-th century in the USSR representations about epidemiology as to a science, communicated, first of all, with studying of epidemic process. It is clear, since revolutions, collectivization and the industrialization, two world wars, then disintegration of the USSR led time and again to economic accident that was accompanied by mass distribution of infectious diseases. Simultaneously the science in the USSR was in relative isolation from world.
During the same historical period in countries of Western Europe and the USA were intensively improved epidemiological analytical researches of the reasons of distribution of noninfectious diseases (cardiovascular and oncological diseases, the diseases connected with deterioration of ecology etc.). Their results began to be used widely in clinical medicine. Epidemiological researches of social influences on health of the person simultaneously developed. Epidemiology it was transformed to a science not about distribution of infectious diseases, and about distribution of illnesses and the factors influencing their distribution. Not epidemic process, and process of distribution of illnesses became object. The methodology of clinical researches has gone deep also. They have allowed to receive trustworthy information about the disease reasons, about efficiency of those or other medical interventions.
The EM methodology is put on a basis epidemiology. Now from the general эпидемиологии it is allocated clinical epidemiology (CE) as science «allowing to carry out forecasting for each concrete patient on the basis of studying of a clinical course of illness in similar cases with use of strict scientific methods of studying of groups of patients for maintenance of accuracy of the forecast». It even name «a science about medicine methodology».
Overall objective of CE is «introduction of methods of clinical research and the analysis of the data providing acceptance of the right decisions» since any science aspires to learn any phenomenon, process or a subject with use of an adequate method.
The epidemiological method is the set of methods intended for studying of the reasons, conditions of occurrence and distribution of illnesses and other conditions in population of people.
In the course of evolution of an epidemiological method 3 basic groups of epidemiological receptions were allocated:
· Descriptive. epidemiological medical illness
· the experimental.
The present short sketch of methodology of researches isn't intended for studying of methods of carrying out of researches. Its purpose - to give to the reader the knowledge necessary for critical reading of messages on researches, i.e. for the most important skill for EM practice.
The basic scientific categories in CE are concepts of a casual and regular errors which have come to medicine from statistics. The biostatistics - the appendix of statistical methods in biology and medicine - is the important scientific tool of epidemiological researches. The knowledge of its bases is necessary for EM practice as it operates with the quantitative data. Sometimes CE try to reduce to statistical methods of research, but it is erroneous, as statistics, on the one hand, is only the tool of researches, and with another - quite independent science.
Primary goal CE consists in application of principles of carrying out of clinical researches for reception of authentic knowledge and a critical estimation of results of researches with a view of perfection of medical practice.
The main thing in an estimation of results of clinical research - to estimate its design which should be adequate to an object of research. Quality of the developed design characterizes a methodological maturity of the researcher which plans its realization. The understanding of types designs researches is, as a matter of fact, understanding of essence clinical epidemiology.
Key element in approach CE to clinical researches and in EM practice is the approach by outcomes of diseases. In CE the attention that for an estimation of interventions it is necessary to study their influence on such outcomes, as death, discomfort, invalidization, a dissatisfaction of patients is paid. These outcomes name clinically important or important for patients. Outcomes in the form of changes of concentration, density and other signs (substitute outcomes) in EM are considered as not having considerable value for practice.
Fleming T.R. and De Mets D.L., conducting special researches on an example of results cohort researches, have shown that at various diseases use of substitute outcomes as criteria of efficiency of treatment can lead to erroneous conclusions in comparison with the come clinical outcomes.
It is necessary to remember that technologies of EM can't and shouldn't replace completely former principles of clinical practice, they only supplement them and offer new, more effective decisions. From these positions the analysis of a condition of application of technologies of EM in the developed countries is of interest. It shows that real clinical decisions are accepted under the influence of a number of factors, such as features of medical institution, level of preparation of the doctor, preference of the patient, etc. Thus main principle of acceptance of the clinical decision remains a choice of the patient at full informing of the last.
The CE is rather difficult for studying. Nevertheless, without knowledge of its bases the modern expert can't estimate quality of the scientific publication, be guided in the modern information, define the price of the made decision (a parity risk/advantage), reliability of the conducted research and critically to estimate clinical recommendations. As a result, not guided in CE the doctor can't apply methodically competently results of scientific researches to the concrete patient.
In the daily activity the doctor solves a problem of the concrete patient and thus a problem facing the doctor, and its practical experience define a choice of the answer to a clinical question. It knows by sight all patients, collects the anamnesis, conducts researches and bears personal responsibility for each patient. As a result the doctor estimates, first of all, specific features of each patient, and it with the big reluctance unites the patients in groups on risk, the diagnosis, a method of treatment and estimates an accessory of the patient to these groups in terms of probability theories.
Personal experience of the doctor also is important for acceptance of clinical decisions. However the overwhelming majority of doctors doesn't possess sufficient practical experience to distinguish all hardly perceptible, is long proceeding, cooperating processes which take place at the majority of chronic diseases.
Object of studying clinical epidemiology are medical aspects of illnesses. For example, how the symptom and disease, intervention and outcomes are connected. To estimate, it is how much possible to trust results of researches, the doctor should understand, how medical researches should be conducted.
Thus, to the doctor to judge reliability of the clinical information, it is necessary to know the basic concepts clinical epidemiology, also as well as anatomy, a pathology, biochemistry, pharmacology. Therefore now clinical epidemiology it is considered as one of fundamental sciences on which the building of modern medicine keeps.
Clinical epidemiology and social aspects of medical aid.
In connection with introduction in applied medicine of achievements of the modern science, new technologies and medicines, medical aid cost has reached such level at which even the richest groups of the population not in a condition to pay all desirable types of service. At the same time use of new kinds of medical interventions isn't always accompanied by proportional improvement of clinical outcomes. In this connection ways of more careful, generalized estimation of the scientific clinical data which ruko-drivers of public health services for improvement of rendering of medical aid can use are developed.
Nowadays very few people challenges position that medical aid should be based on results of correctly spent researches and to be estimated on the end results taking into account financial expenses which the society presumes. Also each patient is considered as a component of the big groups of similar patients that helps not only to do more exact individual forecasts, but also to choose an optimum way of use of the limited financial resources for help improvement probably большему to a contingent of people.
Substantive provisions and principles clinical epidemiology.
Overall objective CE is introduction of methods of the clinical researches providing acceptance of correct decisions. Thus, certainly, personal experience and knowledge of mechanisms of development of diseases is important. However, it is necessary to consider and other prominent aspects.
¦ In most cases the diagnosis, the forecast and results of treatment for the concrete patient with accuracy aren't defined and consequently should be expressed through probabilities.
¦ Probabilities for the concrete patient is better are defined on the basis of the previous experience which has been saved up on similar group of patients.
¦ It is necessary to take always into consideration that clinical supervision should be spent on free patients in the behavior which are observed by doctors with different qualification and own opinion that can lead to the regular errors conducting to the erroneous conclusions.
¦ Any clinical researches are subject to influence of accident and the result of each research can be deformed a random error.
¦ For reduction of errors at decision-making the doctor should use results of the researches based on strict scientific principles, with application of methods of minimization regular and the account of possible random errors.
Clinical questions and answers to them are based on principles and the concepts resulted further.
The basic questions which puts clinical epidemiology, are: deviations from norm, the diagnosis, frequency, risk, the forecast, treatment, preventive maintenance, the reason, expenses. It those questions which arise both at the patient and at the doctor. They are discussed more often among themselves by doctors and patients.
For CE the greatest interest represent the outcomes having the vital value for patients, and also the medical personnel - death, disease, discomfort, invalidization, a dissatisfaction with treatment. Doctors want to understand, predict, interpret and change these phenomena at treatment of patients.
From other medical sciences CE differs that all these phenomena are studied directly in public, instead of on experimental animals or elements of a human body, such as cultures of fabrics, cellular membranes, receptors and mediators, sequences of nucleinic acids etc. the Biological phenomena can't be considered as an equivalent of clinical outcomes, isn't received yet the direct proof of their interrelation.
The quantitative approach.
In good-quality clinical researches correct ways of measurement as results of less reliable measurements give less authentic proofs should be used. Frequency and weight of clinical outcomes, such as or invalidization, it is possible to present death, illness in numerical expression. Also it is possible to measure functional defect and loss of quality of life. In good-quality researches should be considered unreliability of the value judgment made the person, and on this unreliability the amendment should be made.
With split-hair accuracy to predict a clinical outcome it is possible rather seldom. More often on the basis of results spent before researches on similar patients the probability of this or that outcome is defined. At the clinic-epidemiological approach it is supposed that clinical forecasts aren't certain, but can be described quantitatively in the form of probabilities. For example, symptoms of an ischemic heart trouble arise at 1 of 100 men of middle age in a year; smoking increases twice risk of death at any age.
Populations and samples.
Population is big group of the people living in certain geographical region (for example, in Kazakhstan) and reproducing in a number of generations. It is the general biological definition of population, in application to the person it is a population synonym. In эпидемиологии and in clinic population name also any group of persons, possessing some general sign (for example, persons are more senior 65 years, or workers of hotels). Population can represent only some part of the population (for example, in epidemiological researches of the reasons of diseases). It can consist of the patients hospitalized in certain clinic or from patients with certain disease (that takes place in clinical researches is more often). Hence, it is possible to speak about the general population, hospital population or population of patients with concrete disease.
Sample is specially selected part of population. Clinical researches are usually carried out on samples as to investigate all population it is impossible and there is no usually a necessity. That sample reflected population correctly (was representative, i.e. representative), it should be correctly created. In the elementary case it is casual sample of population. Actually, for various reasons in a random way to select members of population it is not always simple, therefore are applied more or less difficult (in comparison with simple sample) receptions. Besides, sample should be enough big that the estimations received on it, for example, frequencies of events, have appeared exact enough. The necessary size of sample is expedient for defining before the beginning of researches by means of standard statistical formulas.
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