MINISTRY OF HEALTH OF UKRAINE VDNZU "UKRAINIAN MEDICAL DENTAL ACADEMY" MINISTRY OF HEALTH OF UKRAINE VDNZU "UKRAINIAN MEDICAL DENTAL ACADEMY" Department of Social Medicine, organization, economyDepartment of Social Medicine, organization, economy

Health of biostatistics and medical jurisprudence Health of biostatistics and medical jurisprudence

Lectures:Lectures:"Clinical Epidemiology."Clinical Epidemiology.

Modern principles and rules of Modern principles and rules of conducting of clinical researchconducting of clinical research“

The subjects of Epidemiology are:The process of the emergence

and spread of any pathological conditions in humans (in the population);

Health status (inability emergence and spread of pathological conditions).

Epidemiology is the study of the distribution of health-related states or events in specified populations and the application of this study to the control of health problems (CDC).

Epidemiology:Epidemiology:  

"Epi" - upon, "demos" - the people, "logos" - study of. The logical, "Epi" - upon, "demos" - the people, "logos" - study of. The logical, systematic approach to understanding the complexities of disease systematic approach to understanding the complexities of disease (Torrence, 1997). The logic of observation and the methods to quantify (Torrence, 1997). The logic of observation and the methods to quantify these observations in populations (groups) of individuals. Epidemiology these observations in populations (groups) of individuals. Epidemiology is the study of the distribution of health-related states or events in is the study of the distribution of health-related states or events in specified populations and the application of this study to the control of specified populations and the application of this study to the control of health problems (CDC). health problems (CDC).

Epidemiology includes Epidemiology includes

1) the methods for measuring the health of groups and for 1) the methods for measuring the health of groups and for determining the attributes and exposures that influence determining the attributes and exposures that influence health; health;

2) the study of the occurrence of disease in its natural 2) the study of the occurrence of disease in its natural habitat rather than the controlled environment of the habitat rather than the controlled environment of the laboratory; and laboratory; and

3) the methods for the quantitative study of the distribution, 3) the methods for the quantitative study of the distribution, variation, and determinants of health-related outcomes in variation, and determinants of health-related outcomes in specific groups (populations) of individuals, and the specific groups (populations) of individuals, and the application of this study to the diagnosis, treatment, and application of this study to the diagnosis, treatment, and prevention of these states or events. prevention of these states or events. (Last, 1995)(Last, 1995)

The purpose of epidemiological studiesTo answer the questions:

1.Descriptive (Observational) Epidemiology: The most basic form of epidemiology, which is the description of the patterns of occurrence of health-related states or events in groups; answering the questions of "Who?", "What?" "Where?", and "When?". Descriptive epidemiology is usually one of the first things done at the scene of any disease outbreak.

2. Analytical Epidemiology: The design, execution and analysis of studies in groups to evaluate potential associations between risk factors and health outcomes to answer the question "Why?".

Brief summaries illustrating the contributions Brief summaries illustrating the contributions of epidemiology to public healthof epidemiology to public health

TopicTopic Brief summaryBrief summaryTopic Brief summary

Childhood cancers Studies analysed risk factors for childhood cancers. One prominent finding was a strong association between abdominal X-rays of pregnant women and leukaemia in children.

Heart disease Community-based longitudinal study in Framingham, Massachusetts, USA showed the association of ischaemic heart disease with hypertension, level of serum cholesterol and other risk factors

Some of the variables used to discribe the Some of the variables used to discribe the distribution of disease in descriptive distribution of disease in descriptive

epidemiologyepidemiologyPeople Age, sex, marital status Race, ethnic group, religion

Occupation, education, cocioeconomic status, Personal habits – use of alcohol and tobacco

Place Climatic zones, Country, region, state, district, urban or rural, local community, city wards, precise location an in institution

Time Year, season, day, secular trends, periodic changes, seasonal variations and other cyclical fluctuations

The main types of epidemiological The main types of epidemiological observationsobservations

1.1. Observational study Observational study (study without the (study without the intentional intervention by the researcher)intentional intervention by the researcher)

Descriptive.Descriptive. Analytical (the most famous are cross-sectional, Analytical (the most famous are cross-sectional,

cohort and studies of "case-control").cohort and studies of "case-control").22 Experimental research Experimental research - a comparative study with - a comparative study with

the intentional intervention in one of the studied the intentional intervention in one of the studied groups (randomized clinical studies).groups (randomized clinical studies).

The basic principle of clinical epidemiology is

that the subject of evaluation is the definite

clinical results

disease discomfort disability death

Clinical Epidemiology: The application of the logical and quantitative concepts and methods of epidemiology to problems (diagnostic, prognostic, therapeutic, and preventive) encountered in the clinical delivery of care to individual patients. The population aspect of epidemiology is present because these individual patients are members of conceptual populations. "A basic science for clinical medicine" (Sackett et al.).

Design of clinical research - plan for its implementation

The choice of research method

Clinical studies in the same group (everyone gets one experimental treatment) - the aim is to compare the previous state

A clinical trial in parallel groups (different groups receiving different treatments)

Choice Contingent (object of study)

Population study

This study is conducted in the volume of the entire population (General totality), which is often referred to in Epidemiology term population study

(Morbidity on the Earth)

Sample study

Sample size (sample) - part of a population that is representative illustration (reduced model) of the population (general totality).

The goal of sample surveys to get

representative information that can be extrapolated to the entire population.

Sampling Frame > Sampling Sampling Frame > Sampling Unit > Sampling FractionUnit > Sampling Fraction

In statistics, a sample group can be In statistics, a sample group can be defined as a subset of a population. The defined as a subset of a population. The population, or target population, is the population, or target population, is the total population about which information total population about which information is required.is required.

Types of SamplingTypes of Sampling

1. Non-Probability Sampling1. Non-Probability Sampling 2. Probability Sampling2. Probability Sampling

Randomization is a sampling method used in scientific Randomization is a sampling method used in scientific experiments. It is commonly used in randomized experiments. It is commonly used in randomized

controlled trials in experimental research.controlled trials in experimental research.:

In medical research, randomization and control of trials is used to test the efficacy or effectiveness of healthcare services or health technologies like medicines, medical devices or surgery.

Probability Sampling and Probability Sampling and RandomizationRandomization

Probability sampling is a sampling technique Probability sampling is a sampling technique wherein the samples are gathered in a wherein the samples are gathered in a process that gives all the individuals in the process that gives all the individuals in the population equal chances of being selected.population equal chances of being selected.

In this sampling technique, the researcher must In this sampling technique, the researcher must guarantee that every individual has an equal guarantee that every individual has an equal opportunity for selection and this can be achieved opportunity for selection and this can be achieved if the researcher utilizes if the researcher utilizes randomization..

Types of Probability SamplingTypes of Probability Sampling

Simple Random SamplingSimple Random Sampling Stratified Random SamplingStratified Random Sampling Systematic Random SamplingSystematic Random Sampling Cluster Random SamplingCluster Random Sampling Mixed/Multi-Stage Random SamplingMixed/Multi-Stage Random Sampling

The sample size of a statistical Sampling is the The sample size of a statistical Sampling is the

number of observations that constitute number of observations that constitute it. it.

n – number of observations N - number of the general population (totality) t - test the reliability δ - standard deviation p - the percentage of events that occurs q = 100 - p   Δ2 - Boundary bias . Boundary bias is usually taken equal to 5% (0.05).

n=2

2 ..

qpt

222

22

tN

Ntn

Analytical epidemiologyAnalytical epidemiology

Two types of study are employed:Two types of study are employed:

Case-control studies (retrospective studies Case-control studies (retrospective studies or case-history studies)or case-history studies)

Cohort studiesCohort studies

Case StudyCase Study

A case control study is a method A case control study is a method extensively used by the medical extensively used by the medical profession, as an easy and quick way of profession, as an easy and quick way of comparing treatments, or investigating comparing treatments, or investigating the causes of disease.the causes of disease.

A cohort study is a research program A cohort study is a research program investigating a particular group with a certain investigating a particular group with a certain

trait, and observes over a period of time.trait, and observes over a period of time.

Retrospective Cohort StudyRetrospective Cohort Study Prospective Cohort StudyProspective Cohort Study Ambidirectional Cohort StudyAmbidirectional Cohort Study

Description of methods

General totality

SamplingComparison of the results

Group control

Observer Group

Evaluation of reaction

Evaluation of reaction

Analysis of case-control studiesAnalysis of case-control studies

Exposure Incidence

Exposed (+)

Not exposed

(-)

Disease (+)

A B A/(A+B)

No disease (-)

C D C/(С+D)

Analysis of cohort studyAnalysis of cohort study

Disease Incidence

Present(+) Absent(-)

Exposed (+) A B A/(A+B)

Not Exposed( -)

C D C/(С+D)

The reliability of the research results

Estimate the reliability of the research Estimate the reliability of the research results - means to establish the probability results - means to establish the probability prediction, ie, to determine with what prediction, ie, to determine with what probability may transfer the results obtained probability may transfer the results obtained on the sample, the entire general population on the sample, the entire general population or other studies.or other studies.

Validity and ReliabilityValidity and Reliability

Validity and ReliabilityValidity and Reliability The principles of validity and reliability are fundamental The principles of validity and reliability are fundamental

cornerstones of the scientific method.cornerstones of the scientific method. Together, they are at the Together, they are at the core of what is accepted as scientific proof, by scientist and core of what is accepted as scientific proof, by scientist and philosopher alike. alike.

By following a few basic principles, anyBy following a few basic principles, anyexperimental design will stand  will stand up to rigorous questioning and skepticism.up to rigorous questioning and skepticism.

What is Reliability?What is Reliability? The idea behind The idea behind reliability is that any is that anysignificant results must be more  must be more

than a one-off finding and be inherentlythan a one-off finding and be inherentlyrepeatable..

What is Validity?What is Validity? Validity encompasses the entire experimental concept and establishes Validity encompasses the entire experimental concept and establishes

whether the results obtained meet all of the requirements of the whether the results obtained meet all of the requirements of the scientific research method.scientific research method.

Any research can be affected by different Any research can be affected by different kinds of factors which, while extraneous kinds of factors which, while extraneous to the concerns of the research, can to the concerns of the research, can invalidate the findings" (Seliger & invalidate the findings" (Seliger & Shohamy 1989, 95).Shohamy 1989, 95).

Склад оцінки результатів дослідження

Визначення помилки Визначення помилки

репрезентативностірепрезентативності

(середніх помилок (середніх помилок середніх середніх арифметичних і арифметичних і відносних величин).відносних величин).

PPген = = PPвыб ± ± tmtm (для относительных показателей),

ММген = М = Мвыб ± ± tmtm (для средних величин), где Рген и Мген - искомые генеральные

параметры частоты и среднего уровня,

Рвыб и Мвыб – найденные выборочные показатели,

m – ошибка представительности,

t – доверительный критерий.

nm

n

qрm

Визначення довірчих Визначення довірчих меж середніх (або меж середніх (або відносних) величин.відносних) величин.

Показник вважається достовірним, якщо він перевищує свою помилку в 3 рази

ПрикладВизначити ефективність щеплення вакциною А.

Вакциновано 400 чоловік, з них 12 захворіло (3%)

Прийнята ймовірність 95,5% (t =2)або 99,7 (t=3)

P ген. сукуп. = Р виборки ± t * m Висновок: При застосуванні для щеплення вакцини А.

захворюваність для генеральної сукупності буде складати

Р = 3,0 ± 2 * 0,85% = ±1,7 (от 1,3% до 4,7%)

%85,0400

)3100(3

m

Порівняння різних сукупностейз використанням параметричних методів

22

21

21

mm

ХХtср

22

21

21

mm

РРtотн

ВИКОРИСТОВУЮТЬ при нормальному розподілі варіант у сукупності

t - критерий точности, Стьюдента (Вильямса Госсета)t ≥ 2 вероятность безошибочного прогноза 95% и более (р <0,05)t < 2 вероятность безошибочного прогноза менее 95% (р >0,05)

Порівняння різних сукупностейз використанням непараметричних методів

Різниця між пов'язаними групами

1. Критерій знаків дляпорівняння груп спопарно пов'язанимиваріантами2. Критерий Вілкоксона

Різниця між непов'язаними групами

1. Критерий Манна—Уитни

2. Критерий Колмогорова-Смирнова 

Для порівнянні більше двох показників, для оцінки якісних ознак :

Використовують критерій відповідності- Пирсона (х2) – хи квадрат

При перевірці статистичних гіпотез

використовуються два поняття Нульова гіпотеза

(гіпотеза про схожість

відмінностей)- Передбачаємо, що

відмінностей немає- Збираємо данні та

оцінюємо- якщо ймовірність

мала – гіпотеза відкидається

Альтернативна гіпотеза

(гіпотеза про

наявність

відмінностей)

Критерій знаків для порівняння груп спопарно пов'язаними варіантами

1. Розрахунок1. Розрахунок2. Порівняння з граничними 2. Порівняння з граничними

табличними данимитабличними даними3. Висновок: 3. Висновок:

Не можна зробити висновок про суттєвість динаміки (р≥0,05)

Можна зробити висновок про суттєвість динаміки (р ≤0,05)

№ п/п ШОЕШОЕ Спрямованість різниці1 день1 день 10 день10 день

11 1313 2323 ++

22 2222 1515 --

33 1616 1818 ++

44 2020 1414 --

55 1919 1111 --

66 2525 1313 --

77 2323 1212 --

88 2020 1313 --

99 1717 1818 ++

1010 1818 1818 ==

Z=3Z=3

В епідеміологічних дослідженнях найчастіше виявляють причино -

наслідкову залежність захворюваності

та передбачуваної причини

Оцінка взаємозв'язку ознак у статистичній сукупності

1.Оцінка напрямку і сили зв'язку між ознаками1.Оцінка напрямку і сили зв'язку між ознаками

2.Оцінка кількісної залежності величини однієї 2.Оцінка кількісної залежності величини однієї ознаки від зміни величини іншоїознаки від зміни величини іншої

Форми прояву кількісних зв'язків

КореляційнаЗначенню кожній

величини ознаки

відповідає декілька

значень іншого

пов'язаного признака

ФункціональнаПри якій значенню

одної з ознак

відповідає суворо

певне значення іншої

(для фізико-хімічних

процесів)

Кореляційний зв’язок

Сила зв'язку Напрямок зв'язку

Пряма (+) Зворотна (-)

Слабка (низька) Від 0 до + 0,29 Від 0 до - 0,29

Середня Від + 0,3 до + 0,69 Від – 0,3 до – 0,69

Сильна (висока) Від + 0,7 до +0,99 Від – 0,7 до – 0,99

Повний зв'язок + 1 - 1

Оцінка напрямку і сили зв'язку між ознаками