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PSM MBBS > Epidemiology > Flashcards

Epidemiology Flashcards

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

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

Epidemic

classification

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

Sites of epidemic depends on

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

Types of observational study

A
  1. Case study
  2. Case series
  3. Cross-sectional
  4. Case control: retrospective
  5. Cohort study
25
Q

Concurrent and non concurrent cohort study

A

Non-concurrent cohort: fixed study population
Concurrent cohort:
• variable/ dynamic study population
• positive association with time trend of the disease

26
Q

Nested case control study

A

A type of cohort study
Nesting of case control within a cohort
Advantage: better analysis
Study of choice for rare and expensive investigations

27
Q
  1. Simple cohort study
  2. Retrospective cohort study
  3. Ambispective cohort study
A
  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
Q

Biases seen in cohort study

A
  1. Attrition bias: failure to follow-up
  2. Hawthorn effect
  3. Selection bias
    No recall bias
29
Q

Types of non-randomized experimental trials

A 
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
Q

Randomized clinical/control trials

features

A
  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
Q

Cross over study design

Multi factorial study design

A

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
Q

Types of randomized interventional trials

A
  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
Q

Preventive trial /
Vaccine trial

Risk factor trial

A

On healthy individuals in field trials

Objections of the study is to keep the risk factor under control, to prevent the disease

34
Q

Attrition
Cross over/ contaminant
in a RCT

A

Attrition:
people who were lost in follow-up of a study
Cross-over/ contaminant:
people who cross over to the opposite group

35
Q

Per protocol analysis

Intention to treat analysis

A
  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
Q

Different types of bias

A
  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
Q

Berksonian bias

A

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
Q

Hawthorne effect

Neyman bias

A

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
Q

Golem effect 🆚 Pygmalion effect

A

Golem effect: blunted effect of research when the researcher is unmotivated

Pygmalion effect: the opp

40
Q

Blinding

A 
Treatment of bias
Types:
1. Single blind:  subject
2. Double blind: M/C
 Subject + doctor
3. Triple blind:
 Subject + doctor + analyzer 
 Most effective
41
Q

Confounding 🆚

Effect modification

A

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
Q

Treatment of confounding

A
  1. Known: by matching
  2. Unknown:
    • randomization
    • standardization
    • stratification
    • regression
43
Q

Types of association

A 
1. Direct association:
• one-to-one 
• multifactorial
2. Indirect/non-causal association
3. Spurious association
44
Q

Causal association or Hill’s criteria of causality

A
  1. Biological plausibility
  2. Coherence of association
  3. Specificity of association
  4. Validity of association
  5. Temporality
  6. Strength of association
45
Q

Hierarchy of association

A
  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
Q

Types of evidence based medicine

A
  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
Q

Types of screening

A
  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
Q

Latent period

Lead time

Screening time

A

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
Q

Lead time bias

A

An apparent 🔼 in survival rates because of higher prevalence and an investigation with long lead time without change in treatment modality

50
Q

Difference between screening test and diagnostic test

A 
Screening test:
 Sensitivity
 🔽 false negative
Diagnostic test:
 Specificity
 🔽 false positive
False positive errors are much more dangerous than false negative

PSM MBBS (5 decks)

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