Third Session Epidemiology

Chapter 15- Cause and Causal Inference

1) What is cause?

Answer: It is anything that bring outcome. It can be either [E]= Cause, Event, Characteristic

2) What are the differences between cause and association?

Answer: Association is first step to establish a cause. An association is bi-direction relation while cause only one direction relation in which more stronger relation.

3) Which of statement is wrong?

a- Cause: alteration in frequency of event will follow change in the other

b- Non-Cause and association is the same

c- Association: not always indicate cause-effect relationship

d- Non-cause: not show the co-existence instead only show cause and effect

Answer: Association and non-causal is the same (at lease for this level). Both not always indicate cause-effect relationship and will apparently show co-existence.

4) Which statement is true?

a- Statistically significant is a cause

b- First step of causality is determine the causal

c- Internal validity is not due to system error

d- External validity is due to random error

Answer: C- Formula in the van diagram. Bias and co-founder exist in external validity and thus not exist in internal. Chance exist in internal validity and thus not exist in external validity.

5) From previous chapter, what do you understand about validity?

Answer: It is part of a measurement and/or a variable. Variable should (down) error, (up) validity, and (up) reliability. In validity it consist of sensitivity, specificity, PPV, NPV, incidence and prevalence etc.

6) Why is it error need to be reduced?

Answer: Because it will distort the result (true value) such that over estimate/ under estimate. Thus not accurate.

7) How do you eliminate error?

Answer: Chance (a)- By using p value statistically significant. Bias (B)- by removing selection and information biases. Co-founder (C)- by Matching, randomization, restriction, multivariate and stratified analysis. By eliminating/reduce the error it automatically establishing the association relationship.

8) How do you establish causal Inference?

Answer: After establishing association, causal is then established by using Hills Criteria (T.A.P.E.R.[s]). Temporal, Association, Probable, Experimental, Relation, coherent, consistent, Specific

9) What is the type of bias?

Answer: 1)Selection Bias formula [AR^S]- Attrition, Response, Voluntary, length, Self. 2)Information bias- Miss-classification (ie: Predicted(non-different) and non-predicted(non-different)) and leads bias.

10) What is co-founder?

Answer: It is a systematic error introduced into the system such that changes in X may not cause change in Z because of the existence of Y. Characteristic of co-founder(Y) include: 1)It is a risk to the outcome, 2) It is association to exposure, 3) it must be no a intermediate factor.

11) Why is this research do multivariate analysis?

a- chance

b- bias

c- co-founder

d- all the above

e- none the above

Answer: C- multivariate analysis is measure to control co-founder, similar to restriction, matching, randomization and stratified analysis.

Chapter 16- Ethic

1) What is the element in ethic?

Answer: Benefit, Justice, respect

2) In your country what is the key element in ethic?

Answer: Investigator, Sponsor, IRB, and MREC

Chapter 17- Prevention and Control

1) What the different between prevention and control?

Answer: Prevention is measure to reduce risk at person level (P), while control is a measure to reduce risk at community level (C).

2) Describe LETS (Level, Effect, Target, Stage) in Prevention and Control ?

Answer:

3) How do you do prevention and control in your opinion?

Answer: Formula [S.I.T.E]- 1-study the disease: agent, host, environment, 2-Investigation, 3-Terminate the source/exposure/risk 4-Educate the population.

4) Which of the following is not epidemiological triad?

a- Host

b- Agent

c- Environment

d- Vector

e- All of the above

f- None of the above

Answer: D- Vector is part of environment as it is not multiplying (in general) just mature in the vector.

5)Draw the chain of infection

Answer: Host--------------Agent-------------Environment

| |

Portal Entry--- Mode Transmission----- Portal Exit

6) Describe the different between Pathogenicity, Infectivity and virulence?

Answer:

7) What the different between antigenicity and immunogenicity?

Answer: Antigenicity is non-specific while immunogenicity is specific response by host

8) In your opinion among all 4 preventive level which is the most important?

Answer: Primary prevention- It have 2; general promotion and specific individual. In General promotion e.g.: Chlorination, ventilation etc. In Specific Individual e.g.: Vaccination. Thus, the prevention has saved millions of lives.

9) Which of the following is correct for pathogenicity and infectivity in polio?

[Pathogenicity] [Infectivity]

a- High High

b- High Low

c- Low High

d- Low Low

Answer: C- Polio primary AR is low but its secondary AR is high.

10) Give example of disease which have high pathogenicity and infectivity?

Answer: Measles- It has high for both. However, in term of virulence its low (less fatal). Example disease which has all high are rabies and AIDS.

11) What the different between Eradication and elimination?

Answer: Elimination (L) is reduction of cases to pint of great rarity at local level (L) where eradication (r) is at global level (G). Extinction is total inhalation of cases. This only

applicable when human is only host reservoir.

12) What are the different between quarantine and Isolation?

Answer: Isolation is separation of sick individual; Quarantine is separation of healthy individual.

Chapter 18- Surveillance

1) What is main purpose of surveillance

Answer: To facilitate the disease control and prevention

2) In your country what are different type of surveillance system?

Answer: Mandatory notification, Syndromic, Sentinel, Laboratory and veterinary

3) In Philippines what kind of surveillance system they used?

Answer: Philippines Integrated Disease Surveillance & Response (PIDSR)

Chapter 19- Screening

1) What is Screening?

Answer: Its method of presumptive to an apparently well individual to identify unrecognised state of disease through intervention which can be rapidly applied.

2) What is characteristic of disease suitable for screening?

Answer: Formula [G.0.L.D]- Grave, not-Late, Long Preclinical, Detectable

3) What is characteristic of screening test?

Answer: Formula [A.B.C.D.R4]- Acceptable, Beneficial, Cheap, No-Discomfort, Reliable, Rapid, Responsive, no- Risky

4) What is factor to be consider in evaluating the screening?

Answer: Feasibility (A.B.C.D) and Effectiveness. In feasibility: Acceptable (Number/proportion), Benefit (PPV), Cheap (Total Cost), no-Discomfort (Follow-up rate)

5) What is different type of screening?

Answer: Mass screening, Opportunistic screening, Targeted screening, and Multiphasic screening.

6) Is multiphasic and multiple screening the same?

Answer: No. Multiple screening apply different test but same disease. But multiphasic using different test and disease.

7) How do you calculate intersection number in Van Diagram of Screening?

Answer: Tp x Sn (True positive x Sensitive of other test) . It can also be used in specificity with True negative.

8) Draw Vann Diagram for simultaneous/ parallel screening?

Answer:

9) Draw Vann Diagram for sequential/ serial screening?

Answer:

10) Is screening used for diagnostic?

Answer: No- It is not for sick individual only for apparently well individual.

Chapter 20- Outbreak Investigation

1) What is outbreak and what its synonym?

Answer: Outbreak is any excess in cases. Its synonym with epidemic and cluster.

2) How outbreak differ from epidemic?

Answer: When previous data is known it is either outbreak or epidemic but if unknown it is cluster. When only one small locality is considered it is outbreak but if more/large it is epidemic.

3) When is outbreak is mounted?

Answer: When there is political, economic, social, technological, legal and environmental involvement.

4) When should outbreak be favourable compare over control and prevention?

Answer: Whenever the source/ mode of TRANSMISSION is unknown, then it is favourable to do investigation despite knowing the causative agents.

5) List the steps involved in outbreak investigation in sequence?

Answer:

1- Preparation of field work

2- Establish existing case (through standard case definition)

3- Validation of cases

4- Establish new case definition for outbreak

5- [S.I.T.E]- Study

6- Investigate}

7- Investigate} Identify: Hypothesis (Develop H, Evaluate H, Refine H)

8- Investigate}

9- Terminate: Prevention and control

10- Education: Disseminate Information

6) Which of the following is step 1?

i- Administrative, ii- Personal worker, iii-Patient, iv-Proforma form

a- i, ii, iii

b- i, iii, iv

c- i, ii, iv

d- None of the above

Answer: C- Step 1 is preparation of field work which involved any administration and work force personal required.

7) What is step 2? what objective of investigation?

Answer: It is the used of standard case definition. Objective same: Study, Identify, Terminate, Educate. To establish existence is to compare with previous known data.

8) What is step 3?

Answer: To validate the cases

9) What is step 4?

Answer: Establishing new case definition for outbreak. It involves time, place and person. Initially this case definition is loos and more sensitive. Subsequently it is more thigh and specific. Stratified case to probable, suspected and confirm. Confirm case only when there is laboratory evidence). No Exposure is included yet at this stage.

10) What is step 5?

Answer: conducting descriptive epidemiology (statistic). Time= Epidemiology curve, Place= Map, and Person= Age/Sex

11) List different type of epidemic curve with example?

Answer: point source (Food borne), Continuous common source (water borne), Intermittent Common source (Legionella), and Propagated (H1N1, Swine, SARS Avian etc)

12) What is step 6,7,8?

Answer: Identification, involved developing the hypothesis (OR/RR/RD), evaluate the hypothesis (Qualitative/Quantitative/lab) and refine the hypothesis. This also steps exposure and causal are established.

13) Step 5 had been considered the most important among others. In your opinion, why?

Answer: Investigation conduct descriptive study to be [R.E.S.T]- Range, Extend, Source, Transmission (IP/Agent-Host-Environment/Hypothesis generating). During this epidemic curve is established.

14) What the usefulness of epidemiological curve?

Answer: It is useful as it: Possible exposure, Nature transmission, Future course and Effectiveness of control prevention.

15) What is step 9?

Answer: termination by control and prevention. Again, it involves REST. And SITE

16) What is step 10?

Answer: Education and dissemination of information through various stakeholder including written report.