epidemiology
1. Definition of Epidemiology : Epidemiology is a science that studies the distribution of diseases and health conditions in the population and their influencing factors, so as to formulate and evaluate strategies and measures to prevent, control and eliminate diseases and promote health.
2. Modern definition and understanding :
①Three levels: disease, disability, and health ②Three stages: reveal the phenomenon, find out the cause, and provide measures ③Three categories: description, analysis, experiment ④Three methods: observation method, experiment method, mathematical method ⑤Three Major elements: principles, methods, applications
3. Important viewpoints of epidemiology : ① group viewpoint (basic); ② comparative viewpoint (core); ③ probability theory viewpoint (characteristics).
4. Epidemiological research methods: observation method, experiment method, mathematical method.
5. The application of epidemiology: <1> To study the laws of population health, disease growth and decline, and changes in disease characteristics.
<2> Diagnose community and population health. <3> Used for health decision-making and evaluation.
<4> Reveal the complete natural history of the disease.
<5> Use epidemiological methods to explore the etiology of diseases of unknown cause. <6>Disease prevention <7>Effect evaluation of disease diagnosis, treatment and prevention methods or measures.
4. Three distributions of diseases : use disease frequency as a measurement index to describe and analyze the distribution of diseases (morbidity, prevalence, mortality, etc.) in different regions , at different times , and in different groups of people . "
The distribution and descriptive research of the second and third chapters
1. Incidence indicators
(1) Incidence rate : refers to the frequency of new cases of a certain disease in a certain population in a certain area and within a certain period of time .
Incidence rate = the number of new cases of a disease in a certain population in a certain period of time / the number of exposed population in the same period × k
k =100%,1000‰……
(2) Attack rate: The attack rate and the incidence rate are also frequency indicators for measuring new cases.
Attack rate = number of new cases of a disease during the observation period / number of exposed population during the same period × k
k =100% or 1000‰
Attack rate: It is generally used to measure small-scale, short-term incidence rates, and the observation time is based on months, weeks, days , or an epidemic period.
(3) Prevalence rate : Also known as prevalence rate or prevalence rate, it refers to the proportion of new and old cases of a certain disease in a certain population within a certain period of time.
Prevalence rate = the number of new and old cases of a certain disease in a certain population within a certain period of time / the number of observed population in the same period × k
2. The difference between the prevalence rate and the incidence rate: ①The numerator of the prevalence rate is the sum of new and old cases of a certain disease in the surveyed population within a certain period of time, while the numerator of the incidence rate is the new incidence of a certain disease in the exposed population within a certain period of time. The number of cases; ②Prevalence is the disease frequency obtained from cross-sectional surveys, which is a static indicator to measure the existence or prevalence of diseases, while the incidence rate is the frequency of diseases obtained from incidence reports or case studies, which is a measure of the occurrence of diseases dynamic indicators.
Factors Affecting Increases and Decreases in Prevalence
| increase decrease |
|
| Prolonged disease course patient life extension Increase in new cases (higher incidence) Case migration healthy people move out Improvement in diagnosis Increased reporting rate |
shortened course of disease Increased fatality rate Fewer new cases (falling incidence) Case moved out healthy people move in Increased cure rate |
Prevalence rate = incidence rate × course of disease
3. Death indicators
(1) Mortality rate : refers to the proportion of the number of people who died of all causes in a certain group of people within a certain period of time. It is the most commonly used indicator to measure the risk of death in a population.
Mortality rate = total number of deaths of a certain group in a certain year/average population of the group in the same year×k
k =1000‰ or 100000/100,000
⑵Case fatality rate : Indicates the proportion of all patients suffering from a certain disease who died due to the disease within a certain period of time. It is mostly used for acute diseases with a short course of disease.
Case fatality rate = the number of deaths due to a certain disease within a certain period of time / the number of confirmed cases of a certain disease during the same period × 100%
4. Common terms used to describe the prevalence of a disease include sporadic, epidemic, and outbreak .
① Sporadic : refers to the general incidence level of a certain disease in the population in a certain area over the years, the cases occur scattered or sporadically in the population, and there is no obvious connection between the cases. Applicable to a large area.
② Epidemic : refers to the incidence rate of a certain disease in a certain area at a certain time significantly exceeds the sporadic incidence level of the disease over the years.
③ Outbreak : In a local area or a group of people in a collective unit, many patients with similar clinical symptoms suddenly appear in a short period of time, which is called an outbreak. Most of these patients have the same source of infection or transmission route, and most patients often appear in the longest incubation period of the disease at the same time.
Survey
1. Current situation research: also known as cross-sectional research, also known as prevalence research or current disease research; to study the relationship between relevant variables (factors) and disease or health status in a specific time point or period and within a specific range of population
2. Characteristics of current situation research: ① Commonly used epidemiological survey methods. ②It is a cross-sectional study in terms of time series. ③It cannot draw conclusions about causality. ④It is generally not used for diseases with a relatively short course of disease .
3. The purpose of current situation research: ①Describe the distribution of diseases or health conditions among the population in a certain area at a specific time
②Provide clues for etiological research ③Determine high-risk groups ④Evaluate the effect of disease detection, vaccination and other prevention and control measures
⑤Used in community health diagnosis ⑥Provide the basis for scientific decision-making by health administration departments
4. Types of current situation research: <1> census <2> sampling survey (sampling method: simple random sampling, systematic sampling, stratified sampling, cluster sampling, multi-level sampling) among which stratified sampling error is the smallest, cluster sampling Maximum error .
5. Determinant factors for determining sample size: <1> expected prevalence rate P<2> allowable error d<3> significant level α
5. Advantages and disadvantages of current situation investigation and research
Advantages : ①Sampling surveys are commonly used, and the results have strong promotional significance
② There is a naturally formed control group from the same group, and the results are comparable
③Multiple factors can be observed at the same time
Disadvantages: ① Difficult to determine the temporal relationship of cause and effect.
②Incidence data cannot be obtained.
③The research object may be in the pre-clinical stage and be mistakenly defined as a normal person.
6. Ecological research : It is a kind of descriptive research. It collects and analyzes data based on the group as the basic unit. relationship between a factor and a disease.
Methods of ecological research: ecological comparative study, ecological trend study. The main shortcoming of ecological research: the ecological fallacy.
Chapter 4 Cohort Studies
1. Queue : refers to a group of people with common characteristics or experiences; divided into fixed queues and dynamic queues
2. Exposure : Refers to being exposed to a certain factor or possessing a certain characteristic.
3. Basic principles : ① Divide the research subjects into exposure group (E) and non-exposure group (Ē) according to whether they are exposed to a certain research factor or its different levels
②Follow up for a certain period of time, and compare the difference in the incidence of the study outcome between the two groups to analyze the relationship between exposure factors and the study outcome
4. Main features: Observation method; establishment of comparison; chronological order; from cause to effect
5. Research type : prospective cohort study; historical cohort study; historical prospective cohort study
The design and implementation steps of the cohort study: ①determining the research factors ②determining the research site ③determining the research population ④determining the sample size
⑤Determination of the research pattern ⑥Determination of confounding factors ⑦Setting of survey forms ⑧Data collection and follow-up
6. Factors affecting the sample size : P0 incidence rate of the disease studied in the non-exposed population or the whole population; P1-P0 difference between the disease incidence rate between the exposed population and the control population; type I error probability α; power 1 -β
7. Basic arrangement mode of data
| cases |
Non-case |
total |
|
| Exposure group |
a |
b |
a+b=n1 |
| non-exposed group |
c |
d |
c+d=n0 |
| total |
a+c=m1 |
b+d=m0 |
a+b+c+d=t |
Incidence rate of exposed group = a/n1 Incidence rate of non-exposed group = a/n0
8. Relative risk
The meaning E is how many times the risk of morbidity or death is that of Ē;
Effect of RR Exposure Exposure and Outcome Association Strength
The farther the RR value is from 1, the greater the effect of exposure and the greater the strength of the association between exposure and outcome
9. Attributable risk AR=Ie-I0=a/n1—c/n0
Significance: ①Compared with population Ē, the number of diseases increased
②The number of diseases reduced after the elimination of AR value exposure factors
10. Attributable risk percentage AR%:
AR%= （Ie-Io）/ Ie×100%
Significance The percentage of morbidity or death in an exposed population that is attributable to exposure to all morbidity or death
11. Population attributable risk PAR=It－I0
Significance: Compared with the general population, the increased incidence of disease in the exposed population
The PAR value reduces the number of diseases after the exposure factor is eliminated
12. Population attributable risk percentage PAR%
PAR%=Pe(RR-1)/ =Pe(RR-1)+1
Significance: PAR as a percentage of all morbidity (or death) in the total population
13. Common biases: selection bias, loss-to-follow-up bias, information bias, confounding bias
14. Advantages of cohort studies: ① directly obtain the morbidity or mortality of the exposed group and the non-exposed group; ② directly estimate the risk;
③ In line with the chronological order, the ability to verify the etiology is strong; ④ Obtain the relationship between one exposure and multiple outcomes;
⑤ The data collected are complete and reliable, without recall bias; ⑥ The natural history of the disease can be studied
Disadvantages: ①It is not suitable for etiological research of diseases with very low incidence; ②It is prone to loss-of-follow-up bias;
③ Time-consuming, manpower, material and financial resources are consumed; ④ Design requirements are strict, and data collection and analysis are difficult;
⑤ During the follow-up, changes in known variables or introduction of unknown variables increase the difficulty of analysis
Chapter 5 Case Control Study
1. Case-control study : According to the disease state, the research objects are divided into case group and control group, and the exposure of the factors studied in the past are respectively traced and compared, so as to speculate whether there is a relationship between the disease and the exposure and the strength of the relationship an observational study.
2. Characteristics of case-control studies: ① Observational method ② Set up control ③ Retrospective, effect-to-cause research ④ Unable to verify the etiology
3. Study type: case and control mismatch; case and control match;
4. Requirements for case selection: ① Reliable diagnosis, use the gold standard ② Select confirmed new cases
5. Selection of controls: in principle, candidates must come from the population of cases; this means that once the disease under study occurs in the control, it can become the research object of the case group.
6. Estimation of sample size Relevant estimates: ① Exposure rate of the factors studied in the population ② RR approximate value OR value (obtained by consulting literature or pre-investigation) ③ α value ④ power
7 OR Calculation and Confidence Limit Estimation and Significance
Ratio of exposed to non-exposed persons in the case group divided by the ratio of exposed to non-exposed persons in the control group
OR Like RR, the odds ratio reflects the degree to which exposed individuals are at greater risk of developing a disease than non-exposed individuals.
Prerequisites: ① The morbidity (death rate) of the disease under study is very low
②If the selected subjects in the case-control study are well represented, the OR value will be very close to or even equal to the RR value
8. Common biases in case-control studies: selection bias, information bias, recall bias, survey bias, confounding bias
9. Advantages of case-control studies:
① Especially suitable for the research of rare diseases and rare diseases;
②Save labor, save money, save time, and be easy to organize and implement
③ It can also be used for vaccine immunological effect assessment and outbreak investigation;
④The relationship between multiple factors and a certain disease can be studied at the same time
⑤No harm to the research subjects
Disadvantages of case-control studies :
① It is not suitable for the study of factors with a very low exposure ratio;
② Selection bias is unavoidable
③ It is difficult to judge the time sequence of exposure and disease, and the authenticity of the information is poor;
④There is recall bias
⑤ Unable to measure disease rates in exposed and non-exposed groups
10. OR: odds ratio: refers to the ratio of the exposure ratio of a certain factor in the case group to the exposure ratio of the factor in the control group, reflecting that the exposure ratio of a certain factor in the case group is several times that of the control group. OR=(a/c)/(b/d)=ad/bc
(1) OR characteristics: Like RR, the odds ratio reflects the degree to which exposed individuals have a higher risk of developing a disease than non-exposed individuals
⑵If two conditions can be satisfied OR≈RR ①The morbidity (death rate) of the disease under study is very low
②The selected subjects in the case-control study are well represented
⑶OR 95%CI=
⑷ Significance of odds ratio
When OR=1, it means that there is no relationship between the exposure factor and the disease.
When OR>1, it means that there is a "positive" exposure-disease relationship between the exposure factor and the disease, and the exposure factor is a risk factor
When OR<1, it means that there is a "negative" exposure-disease association, and the exposure factor is a protective factor
11. Analysis of individual matching design data:
<1> Is there any relationship between exposure and disease:
When b+c>40 =
b+c<40时 <2>
12 types of bias:
(1) Selection bias: The error caused by the difference in certain characteristics between the selected research objects and the non-selected research objects. This bias
Reliance often occurs during the design phase.
(2) Information bias: Systematic error caused by flawed methods of measuring exposures and outcomes in the process of collecting and collating information.
(3) Confounding bias: When studying the association between a certain factor and a certain disease, due to the influence of an external factor that has a restrictive relationship with the disease and is also related to the exposure factor studied, the exposure factor studied is covered up or exaggerated Link to disease.
Chapter 6 Clinical Curative Effect and Disease Prognosis Research
1. Characteristics of clinical curative effect research: characteristics of experimental research, particularity of research objects, consideration of medical ethics issues, and scientific evaluation of clinical curative effect
2. Several principles to be mastered in experimental design: the principle of control, the principle of randomization, the principle of blinding, and the principle of repetition
3. Random classification methods: simple randomization, graded randomization, stratified randomization
4. Application of blind method
<1.>Single-blind, single-blind means that the research subjects do not know their grading and treatment, but the observers and data collectors do.
<2> Double-blind, the research subjects and observers do not know the grouping situation, nor do they know the treatment measures accepted by the subjects.
<3> Triple-blind, the research subjects, observers and data collation analysts are not aware of the grouping and processing of the research subjects.
Chapter VII Evaluation of Diagnostic Tests
1. Gold standard: The most reliable method for diagnosing diseases recognized by the current clinical medical community, also known as standard diagnosis. (results of biopsy/autopsy, surgical findings, microbial culture, special examinations, diagnostic imaging, long-term follow-up)
2. Diagnostic test: Refers to the test method that uses various experiments, medical instruments and other means to examine patients to determine or rule out diseases.
3. Evaluation indicators:
<1> The calculation formula of sensitivity /true positive rate (Se) is: Sensitivity (Se)=[a/(a+c)]×100% Significance: Sensitivity reflects the ability of the diagnostic test to detect cases.
<2> The specificity/true negative rate (SP) calculation formula is: Specificity (SP)=[d/(b+d)]×100% Significance: It reflects the ability of the test to exclude non-cases.
<3> False Negative Rate - Missed Diagnosis Rate: Calculation formula: FN=[c /(a+c)]×100% Significance: The proportion of people who are actually sick but are wrongly judged to be free by the diagnostic test. Sensitivity is complementary to false negative rate, that is, the higher the sensitivity, the lower the false negative rate.
<4> Misdiagnosis rate - false positive rate : The calculation formula is: Misdiagnosis rate = [b / (b + d)] × 100% Significance: Among the cases diagnosed as "no disease" by the true standard, the diagnostic test result is positive The proportion of patients who are actually free of the disease are wrongly judged to be diseased by diagnostic tests. The specificity is complementary to the false positive rate, that is, the higher the specificity, the lower the false positive rate.
<5> Youden index : the calculation formula is: Yi=(Se+Sp)-1
<6>Concordance rate: refers to the percentage of the sum of the number of true positive cases and the number of true negative cases obtained by the diagnostic test in the entire test object, that is, the degree of agreement between the results of the diagnostic test and the results of the gold standard diagnosis. It reflects the ability of a diagnostic test to correctly diagnose patients and non-patients.
The calculation formula is: coincidence rate=[(a+d)/N]×100%
<7> Positive predictive value : It is the percentage of true patients (those diagnosed with a certain disease with the gold standard) among the subjects whose diagnostic test results are positive. For a diagnostic test, the higher the value, the better. Positive predictive value (PV+) = [a/(a+b)]×100%
<8> Negative predictive value is the percentage of true non-patients (gold standard confirmed non-patients) among the negative results of diagnostic tests. The larger the value, the better, negative predictive value (PV-) = [d/(c+d)] × 100%
<9> Positive likelihood ratio
In a diagnostic test, the positive likelihood ratio is the ratio of the true positive rate to the false positive rate, and the larger the ratio, the better the diagnostic method.
LR+=[a÷(a+c)]/[b÷(b+d)]=SE/(1-SP)
<10> Negative likelihood ratio
In a diagnostic test, the negative likelihood ratio is the ratio of the false negative rate to the true negative rate, and the smaller the ratio, the better the diagnostic method.
LR-=[c÷(a+c)]/[ (d ÷[b+d])
4. ROC curve use: used to determine the best critical point; compare the value of two or more diagnostic tests.
5. Joint test
Parallel test: also called parallel test, parallel combined test can be adopted when clinical diagnosis is urgently needed. The result is increased sensitivity, less chance of missed diagnosis, and improved negative predictive value, which facilitates the exclusion of other diagnoses. But the price is that the specificity is reduced, the false positive rate is increased, and it is easy to cause misdiagnosis.
Serial tests: also called tandem tests, when the specificity of several diagnostic methods used is low, a series of tests can be used to improve the specificity of diagnosis and reduce misdiagnosis. Sequence tests increase specificity and positive predictive value at the expense of decreased sensitivity and increased missed diagnosis rate.
Chapter VIII Etiology and Etiology Inference
1. The definition of etiology in modern epidemiology: Those factors that can increase the probability of disease in the population can be considered as the cause of disease. When one or more factors do not exist, the frequency of disease in the population will decrease.
2. Etiology model: triangle model, wheel model, etiology network model
3. The basic conditions for the occurrence of diseases: pathogenic factors, hosts, and environments.
4. Logical method of causal inference: ①hypothetical deductive method ②MILL criterion: ①similar method ②difference method ③common variation method ④analogous method ⑤elimination method
5. Inference criteria for causality: strength of association, chronological order of association, specificity of association, reproducibility of association, dose-response relationship, consistency of factor and disease distribution, biological plausibility of association, experimental evidence, similarity
Chapter 9 Common bias and its control in epidemiological research
1. Systematic error: (Bias) During the research process, an error caused by some known or controllable factors that systematically deviates the research results or inferences from the real situation.
2. Classification of bias: selection bias, information bias, confounding bias.
Chapter 10 Epidemiology of Infectious Diseases
1. Epidemic process of infectious diseases: pathogen, host, infection process and infection spectrum
2. Characteristics of common pathogens: pathogenicity, infectivity, and virulence.
3. The variability of pathogens: ① Drug resistance variation: Mycobacterium tuberculosis ② Antigenic variation: Influenza A ③ Virulence variation: Hantavirus
4. Infection process: refers to the process in which pathogens interact and fight with the body after they invade the body.
5. Spectrum of infection: Refers to the clinical manifestations of varying severity after the body is infected with the pathogen and undergoes the infection process.
Classification: ① Mainly recessive infection ② Mainly overt infection ③ Most infected people end up with death.
6. Epidemic process of infectious diseases: source of infection, route of transmission, susceptibility of the population.
7. Source of infection: Refers to a person or animal that has pathogens living and multiplying in their body and can excrete them. Including infectious disease patients, pathogen carriers and infected animals.
Classification: ①Infected people: patients, pathogen carriers ②Infected animals ③Infected people
8. Patients as the source of infection are divided into: ① incubation period clinical symptom period ② recovery period ③ infection period
9 Epidemiological significance and application of the incubation period:
<1> Determine when the patient was infected, trace the source of infection, and find out the route of transmission.
<2>Determine the period of detention for inspection, quarantine and medical observation of contacts.
<3> Determine the time of immunization.
<4>Evaluate the effect of preventive measures.
<5> The length of the incubation period can also affect the epidemic characteristics.
10 Pathogen carrier: Refers to a person who does not have any clinical symptoms but can excrete pathogens. Carriers, virus carriers and worm carriers are collectively referred to as pathogen carriers.
Classification: <1> latent pathogen carrier <2> convalescent pathogen carrier <3> healthy pathogen carrier
11. Dissemination characteristics and popular characteristics:
⑴ Airborne transmission: ① Droplet transmission ② Droplet nuclear transmission ③ Dust transmission
Epidemic characteristics of airborne transmission: ① Wide spread and high incidence. ② High incidence in winter and spring ③ More common in children and adolescents ④ In the population without immunization, the incidence is periodic ⑤ High incidence in crowded and densely populated areas
(2) Transmission by water: one is transmitted by drinking water, and the other is transmitted by infected water.
The epidemic characteristics of diseases transmitted by drinking water are as follows: ①The distribution of cases is consistent with the scope of water supply, and there is a history of drinking the same water source; ②Except for breastfeeding infants, there is no difference in age, sex, or occupation; ③If the water source is often polluted, Cases continue throughout the year, and the onset is endemic; ④ After stopping the use of polluted water sources or taking disinfection and purification measures, the outbreak or epidemic will subside.
(3) Epidemic characteristics of food transmission: ①The patient has a history of eating a certain food, and those who do not eat will not get sick; ②The incubation period of the patient is short, and a large amount of contamination can cause an outbreak ③When the contaminated food is stopped, the outbreak will subside quickly .
⑷Transmission by contact ⑤Insect-borne transmission ⑹Transmission by soil: ⑺Iatrogenic transmission:
(8) Vertical transmission: The transmission of pathogens from mother to offspring becomes vertical transmission. include:
Transplacental transmission, ascending sexual transmission, transmission during childbirth
6. Crowd susceptibility : The susceptibility of the population as a whole to infectious diseases becomes the population susceptibility.
⑴The main factors affecting the increased susceptibility of the population: ① Increase in newborns ② Immigration of susceptible population ③ Natural decline of immunity of immune population
④ Death of immune population
(2) The main factors affecting the reduction of susceptibility of the population: ① Planned immunization ② Epidemic of infectious diseases ③ Latent infection
7. Epidemic focus : the area where the source of infection and the pathogens discharged can spread to the surrounding area is called the epidemic focus.
(1) Conditions for forming an epidemic focus: <1> There is an infectious source <2> The pathogen can continue to spread
(2) The following conditions must be met for the eradication of the epidemic foci:
①The source of infection has been removed (such as isolation, death) or the state of excreting pathogens has been eliminated.
② The pathogens disseminated by the source of infection in the external environment are completely eliminated (disinfection, insecticide).
③ All susceptible contacts have no new cases or proved to be uninfected after the longest incubation period of the disease.
8. Factors affecting the epidemic process of infectious diseases: ① natural factors ② social factors
Chapter 11 Disease Prevention and Control
1. Primary health care : (PHC) refers to the most basic health care services that are available to everyone, reflect social equal rights, and are affordable for the people and the government.
2. The main content of China's planned immunization work is "vaccination of five vaccines to prevent seven diseases" .
3. Preventive measures for chronic diseases:
⑴Primary prevention: also known as etiological prevention, it is the measures taken against the etiology (or risk factors) before the disease occurs, that is, "preventing the disease before it happens" Health Promotion Health Protection
⑵Secondary prevention: also known as preclinical prevention, that is, early detection, early diagnosis, and early treatment of "three early" prevention in the preclinical stage of the disease, so as to control the development and deterioration of the disease, and prevent the recurrence or malignant transformation of the disease.
(3) Tertiary prevention: also known as clinical prevention. Refers to taking timely and effective measures for the sick to prevent the deterioration of the disease, so as to prevent complications and disabilities; to promote functional recovery, psychological rehabilitation, and family nursing guidance for the disabled or disabled, so that the patient can resume life and work as much as possible. Ability, and can participate in social activities and prolong life.
Chapter 12 Nosocomial Infection
1. Nosocomial infection: refers to the infection acquired by inpatients in the hospital, including the infection during hospitalization and the infection after discharge from the hospital, but excluding the infection that has started before admission or has been in the incubation period at the time of admission.
2. Classification of nosocomial infections: self-infection, nosocomial infection, brought-in infection, and cross-infection.
Chapter 13 Adverse Drug Reactions
1. Adverse drug reaction: Unrelated or unexpected harmful reactions of qualified drugs under normal usage and dosage.
2. WHO divides adverse drug reactions into three types: A, B, and C
Type A adverse reactions: transitional effects, side effects, toxic effects, secondary reactions, sequelae, first-dose effects, withdrawal reactions
Type B adverse reactions: idiosyncratic reactions, allergic reactions
Type C adverse reactions