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PSM MBBS > Epidemiology > Flashcards

Epidemiology Flashcards

(50 cards)

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1
Q

Infection
Contamination
Infestation

A

Infection:
entry and multiplication of infectious agent in body
Contamination:
Presence of infective agent on a surface
Infestation:
lodgement and development/multiplication of an arthropod on body/clothes

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2
Q

Types of infections

A
  1. Nosocomial
  2. Iatrogenic
    Eg: ADR
  3. Exotic
  4. Opportunistic
  5. Dead-end
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3
Q

Agent determinants

A 
1. Infectivity: invade and multiply
 Attack rate/2° attack rate
2. Antigenic:
 Local immune response
3. Pathogenicity:
 Local inflammatory response or pathological changes
4. Virulence:
 Fatality rate
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4
Q

Amphixenasis

A

Infection from animal to human and vice versa

Eg. trypanosomiasis

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5
Q

Epidemiological triad

A

Agent
Host
Environment

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6
Q

Diseases eradicated in India

A
  1. Small pox
  2. Guinea worm disease
  3. Wild poliomyelitis
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7
Q

Potentially eradicable diseases

A
  1. Measles
  2. Malaria
  3. Poliomyelitis
  4. Leprosy
  5. Yaws
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8
Q

India declared free from the diseases

A
  1. Yaws
  2. Childhood trachoma
  3. Neonatal tetanus
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9
Q

Disease transmission types

A
  1. Direct: D-tics
    droplet, transplacental, inoculation, contact, soil
  2. Indirect: FAV-uv
    Fomite, air, vehicle, unclean hands, vector
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10
Q

Transplacental transmission of diseases

A

TORCH, HIV
Chemicals: thalidomide, stilbesterol, heavy chemicals
1st trimester: rubella
2nd trimester: parvovirus
3rd trimester: syphilis, toxoplasmosis, CMV, hepatitis B
Delivery: hepatitis C, herpes, HIV

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11
Q

Biological transmission of diseases

A
  1. Propagative
  2. Cyclodevelopment
  3. Cyclopropagative
  4. Transovarian transmission
  5. Transtadial transmission
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12
Q

Chemical isolation

Ring isolation

A 
Treatment in homes 🏡 and rendering the patients non-infectious
TB, leprosy, STD
Contacts of swine flu patients
Ring isolation/ ring immunization:
 A type of chemical isolation
 Eg., poliomyelitis, measles, small pox
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13
Q

Investigation of epidemic

A
  1. Verification of diagnosis
  2. Confirmation of epidemic
  3. Defining population at risk
  4. Rapid search for cases
  5. Data analysis
  6. Formulate hypothesis: to find the cause of the disease
  7. Test hypothesis
  8. Evaluate ecological factors
  9. Further investigation for risk
  10. Report writing and dissemination
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14
Q

Wearing the PPE

A

Apron ➡️
mask 😷 ➡️
eye goggles 🥽 ➡️
gloves 🧤

Mask 😷 is always removed last

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15
Q

Survival analysis

A

Tells about probability of surviving over some period.

Using life table analysis and Kaplan Mier analysis

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16
Q

Types of standardization (of rates of different population)

A

Direct standardization:
When age specific death rate and standard population is available
Indirect standardization:
• When age specific death rate or a standard population is not available
• Reference population is considered
SMR = observed deaths/expected death *100

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17
Q

Prevalence

Special prevalence rate

A

Prevalence: total number of cases in a population
Special prevalence rate:
1. Point prevalence
2. Period prevalence

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18
Q

Incidence

Special incidence rates

A

Incidence: number of new cases in a defined population per using time
Special incidence rates:
1. Attack rate
2. Secondary attack rate:
Number of infected individuals from a primary case within one incubation period

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19
Q

Types of epidemiology

A 
1. Observational (non-interventional):
• Descriptive 
• Analytical
2. Experimental (interventional):
• non-randomized trials
• randomized trials
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20
Q

Descriptive epidemiology

A
  1. Defining the population or sample of population
  2. Defining the disease
  3. Describing the disease
  4. Measurement of disease
  5. Comparing with known indices
  6. Formulation of hypothesis
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21
Q

Time fluctuations seen in diseases

Study These Flashcards
A
  1. Short term: epidemic
  2. Periodic: cycles or seasonal
  3. Long term: secular trends
22
Q

Epidemic

classification

Study These Flashcards
A
  1. Slow
  2. Common source:
    • single exposure
    • multiple exposure
  3. Propagated
23
Q

Sites of epidemic depends on

Study These Flashcards
A
  1. Herd immunity
  2. Secondary attack rate
  3. Density or chance of contact with cases
24
Q

Types of observational study

Study These Flashcards
A
  1. Case study
  2. Case series
  3. Cross-sectional
  4. Case control: retrospective
  5. Cohort study
25
Concurrent and non concurrent cohort study
Non-concurrent cohort: fixed study population Concurrent cohort: • variable/ dynamic study population • positive association with time trend of the disease
26
Nested case control study
A type of cohort study Nesting of case control within a cohort Advantage: better analysis Study of choice for rare and expensive investigations
27
1. Simple cohort study 2. Retrospective cohort study 3. Ambispective cohort study
1. A cohort of exposed and unexposed are chosen and followed up for a particular time and assessed for the number of diseased and healthy individuals 2. Calculating the number of diseased and healthy individuals among the exposed and unexposed for past 10 years till date 3. Days has been collected for 8 years. Next 2 years is by prospective study
28
Biases seen in cohort study
1. Attrition bias: failure to follow-up 2. Hawthorn effect 3. Selection bias No recall bias
29
Types of non-randomized experimental trials
``` 1. Pre & post test study designs with or without control: Usually 2 groups 2. Uncontrolled trials: Historical controls (values) 3. Natural experiments: Calamity becomes intervention ```
30
Randomized clinical/control trials | features
1. It removes selection bias 2. It is done at the level of allocation, not done in the level of selection 3. It is known as chance and equal chance
31
Cross over study design | Multi factorial study design
It is classified under randomized trial (but it can be randomized or not) 2 groups, both are subjected to 2 drugs (not simultaneously) separated by a washout period Advantage: 🔽 chance of biological variation Disadvantages: Cannot be done when: 1. Drug has long t1/2 or the drug is curative 2. If disease is acute/fatal
32
Types of randomized interventional trials
1. RCTs 2. mFSD or cross over study design 3. Preventive trial 4. Risk factor trials 5. Cessation experiment 6. Trial of etiological agents
33
Preventive trial / Vaccine trial Risk factor trial
On healthy individuals in field trials Objections of the study is to keep the risk factor under control, to prevent the disease
34
Attrition Cross over/ contaminant in a RCT
Attrition: people who were lost in follow-up of a study Cross-over/ contaminant: people who cross over to the opposite group
35
Per protocol analysis | Intention to treat analysis
1. Per protocol analysis: • The modified group due to -cross-overs and attrition- is taken into account • Not adjusted for randomization 2. Intention to treat analysis: • Original group -irrespective of cross over and attrition- is taken into account • Randomization is preserved
36
Different types of bias
1. Observer bias 2. Interviewer bias 3. Experimental bias 4. Surveillance bias 5. Recall bias 6. Berksonian bias 7. Neyman bias 8. Hawthorne effect 9. Golem effect 10. Pygmalion effect
37
Berksonian bias
Found in case control studies which are hospital based Differential rate of admission in hospitals In certain cases, the cases can be equal to control
38
Hawthorne effect Neyman bias
Hawthorne effect: change in attitudes under observation Usually in follow-up studies It’s a subject bias Neyman bias: differential mortality pattern b/w two groups
39
Golem effect 🆚 Pygmalion effect
Golem effect: blunted effect of research when the researcher is unmotivated Pygmalion effect: the opp
40
Blinding
``` Treatment of bias Types: 1. Single blind: subject 2. Double blind: M/C Subject + doctor 3. Triple blind: Subject + doctor + analyzer Most effective ```
41
Confounding 🆚 | Effect modification
Confounding and effect modification are associated with disease and risk factor Confounding on stratification shows no association Effect modification on stratification shows positive effect
42
Treatment of confounding
1. Known: by matching 2. Unknown: • randomization • standardization • stratification • regression
43
Types of association
``` 1. Direct association: • one-to-one • multifactorial 2. Indirect/non-causal association 3. Spurious association ```
44
Causal association or Hill’s criteria of causality
1. Biological plausibility 2. Coherence of association 3. Specificity of association 4. Validity of association 5. Temporality 6. Strength of association
45
Hierarchy of association
1. Case studies 2. Case series 3. Cross sectional 4. Case control 5. Cohort studies 6. POSD 7. RCT 8. MFSD 9. Systematic review 10. Meta-analysis Increasing downwards
46
Types of evidence based medicine
1. Systematic review: Preliminary study to assess her effect of an intervention/drug Structured approach 2. Meta-analysis: Statistical analysis for final assessment of effect of risk factor/drug/intervention in disease or health status
47
Types of screening
1. Mass screening 2. High risk screening: 3. Multi phasic screening: Two different tests in the same population 4. Presumptive/pricing: Primary level of prevention HIV screening for ANC,… 5. Prescriptive: Early diagnosis PAP smear
48
Latent period Lead time Screening time
Latent period: Onset of pathogenesis to usual point of diagnosis Lead time: 1st possible point of diagnosis to usual point of diagnosis (usually after critical point) Screening time: 1st possible point of diagnosis to critical point of diagnosis • A better investigation is the one with longer lead time and shorter screening time
49
Lead time bias
An apparent 🔼 in survival rates because of higher prevalence and an investigation with long lead time without change in treatment modality
50
Difference between screening test and diagnostic test
``` Screening test: Sensitivity 🔽 false negative Diagnostic test: Specificity 🔽 false positive False positive errors are much more dangerous than false negative ```

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