Epi

Question 1

List the two ways to limit control confounding

Answer 1

1) Study design stage 2) Analysis of data stage

Question 2

Describe randomization in terms of controlling for confounding variables. State weakness and strengths

Answer 2

Randomization technique hopefully distributes an equal # of subjects with the known and unknown confounders into each intervention group.

Strength:
-WIth sufficient sample size (N), randomization will likely be successful in serving its purpose (making groups “equal”)

Weakness:

• Sampel size may not be large enough to control for all known and unknown confounders
• process doesn’t guarantee successful equal distribution between all intervention groups for all known and unknown confounders
• Practical only for interventional studies

Question 3

What is the definition of Epidemiology?

Answer 3

A public health-discipline basic science which studies the distribution and determinants of disease in populations to control disease and illness and promote health

Question 4

What are some epidemiological assumptions?

Answer 4

• Disease occurrence is not random
• Systematic investigation of different populations can identify ASSOCIATIONS and casual/preventive factors and impact of changes can impart on health of populations
• Making comparisons is the cornerstone of systematic disease assessments/investigations

Question 5

What are the 6 core functions of epidemiology?

Answer 5

1) Public health surveillance
2) Field investigation
3) Analytic analysis
4) Evaluations
5) Linkages
6) Policy development

Question 6

What are two components of Distribution?

Answer 6

1) Frequencies

2) pattern (W/W/W)

Question 7

What are the components of determinants?

Answer 7

1) Factors of exposure
2) Etiology of disease
3) Mode of transmission
4) Social/environmental/biologic elements that determine the occurrence /presence of disease
This is analytic epidemiology

Question 8

What is passive surveillance?

Answer 8

Relies on healthcare system to follow regulations on required reportable diseases/conditions

Question 9

What is active surveillance system?

Answer 9

Public health officials go into communities to search for new disease/condition cases

Question 10

What is syndromic surveillance?

Answer 10

A system that looks for the pre-defined signs/symptoms of patients related to trackable-but-rare diseases/conditions

• tracks the occurrence of disease via looking for certain syndrome, symptoms, or signs. Physician and ER see symptoms of the flu: rhinorrhea, body aches, fever etc. Sadly, those are similar to other condition. however there are disease states where they have specific presentation. There’s a collection of system or signs to indicate that specific type of disease and speculate if that is it.
• It’s asking for symptoms connected to the condition that can possibly be diagnosed to the condition.
• -syndormic surivllance is like an active surveilance to look for PRE-DEFINED signs of patients related to trackable disease/conditions

Question 11

What is biosurveillance?

Answer 11

where they take bio samples from animals, plants, and environment to assess the status of the disease.

Question 12

What is Induction period?

Answer 12

Time between exposure and onset of disease

Question 13

What is latency period?

Answer 13

Time between onset of disease and development of symptoms (disease detection)

Question 14

What is case definition?

Answer 14

• It is a set of uniform criteria used to define a disease/condition for public health surveillance
• Enable public health to classify and count cases consistently across reporting jurisdictions
• A case might be classified as suspected or probable while waiting for the laboratory results to become available once the lab provides the report, the case can be reclassified as either confirmed or “not a case’ depending on the results.
• A case definition may have several sets of criteria, depending on how certain the diagnosis is. For example, during an investigation of a possible case or outbreak of measles, a person with a fever and rash might be classified as having a suspected, probable, or confirmed case of measles, depending on what evidence of measles is present

Question 15

Define Epidemic

Answer 15

Occurrence of disease clearly in excess of normal expectancy

• community/period is clearly defined
• goal is to capture disease as early as possible

• For example, epidemic can be across the zip code, entire city. Next year, we could be talking about an explosion of flu cases much higher than year to ear bases. So next year, we talk about epidemic of flu of KC. It can be time , period or space wide in community
o Book: An outbreak or epidemic is the occurrence of more cases of disease more than expected in a given area or among a specific group of people over a particular time. Epidemology defines outbreak as an epidemic limited to localized increase in the incidence of disease such as village, town, or closed instution.

Question 16

Define Outbreak

Answer 16

o An epidemic limited to a localized increase in the occurrence of disease
• Sometimes interchanged with the word “cluster”
• Book: Cluster is an aggregation of cases in a given area over a particular period without regard to whether the number of cases is more expected This aggregation of cases seems to be unusual . for example, the diagnosis in one neighborhood of four adults with cancer may be disturbing to residents but may well be within the expected level of cancer occurrence

Question 17

Define endemic

Answer 17

o Constant presence of a disease within a given area or population in excess of normal elvels in other areas
o Alaways elevated compared to other parts of the global but that’s consistent for them
o (of a disease or condition) regularly found among particular people or in a certain area.

Question 18

Define emergency of international concern

Answer 18

o An epidemic that alerts the world to the need for high vigilance (pre-pandemic labeling)

Question 19

Define pandemic

Answer 19

o An epidemic spread world-wide (global health)
• Muti-national/muti continent affected
• For example: Ebola: defining the epidemic a public heath emergency of international concern. H1N1 flu was an pandemic in 2009.
• This alerts the world to the need for high alert
• The Answer: An epidemic occurs when a disease affects a greater number people than is usual for the locality or one that spreads to areas not usually associated with the disease. A pandemic is an epidemic of world-wide proportions.

Question 20

What is an epidemic curve?

Answer 20

o Visual time-based depiction created during an outbreak/epidemic of the # of cases; by date of reporting
o Book: a simple visual display of the outbreak’s magnitude and time trend.

o It visually depicts:
1) The pattern (shape) of disease spread/occurrence (pattern of spread in population)
• Common/source (continuous & Intermittent)
o NOT person to person spread; derived from a common, single point source for the outbreak
o Book: Persons are exposed to the same source over a relative brief period . in fact any sudden rise in the # of cases suggests sudden exposure to a common source one incubation period earlier

2) Propagated source:
o Person-to-person spread
o I have notes on the slides itself and the textbook about the propagated and common source
• Magnitude and timing of disease occurrence
• Sentinel or index case/peak/outliers
• Start/stop/duration (time)

Question 21

What are 3 elements of bias impact?

Answer 21

1) Source/type
2) Magnitude /strength
3) Direction

Question 22

What are the two main catergoies of bias?

Answer 22

1) Measurement related

2) selection related

Question 23

What is healthy-worker bias. Is it selection or measurement bias?

Answer 23

The healthy user bias is a bias that can damage the validity of epidemiologic studies testing the efficacy of particular therapies or interventions. Specifically, it is a sampling bias: the kind of subjects that voluntarily enroll in a clinical trial and actually follow the experimental regimen are not representative of the general population. They can be expected, on average, to be healthier as they are concerned for their health and are predisposed to follow medical advice, both factors that would aid one’s health. In a sense, being healthy or active about one’s health is a precondition for becoming a subject of the study, an effect that can appear under other conditions such as studying particular groups of workers

Question 24

What is Self selection/participant bias. Is it selection or measurement bias?

Answer 24

Those that wish to participate (volunteer) may be different in some way to those that don’t volunteer or self select (refusal/non-response) to participate .
its selection bias

Question 25

What is control selection bias. Is it selection or measurement bias?

Answer 25

Bias where the control is controlled. Its selection bias
-can easily be seen in case control studies

Control Selection Bias. In a case-control study selection bias occurs when subjects for the “control” group are not truly representative of the population that produced the cases

Question 26

What is Neyman bias. Is it selection or measurement bias?

Answer 26

Selection bias.
The selective survival bias (Neyman bias) occurs in case-control studies when cases are selected from those who have disease, not exclusively from those who are newly diagnosed. The distinction here is between prevalent disease (those with an existing condition) and incident disease (those with a new diagnosis of the condition). Prevalent disses is influenced by factors that cause the disease as well as factors that influence cure or survival. If the study design allows individuals with established disease (prevalence cases) into the study, then the researcher may not be able to distinguish between effects related to cure or survival versus effects related to the likelihood of developing disease.

• more easily descriptive for longer-lasting and more indolent diseases
• not effective for acute or rapidly fatal cases

Question 27

What are two subcategories of measurement bias? and name those in each.

Answer 27

Subjected-related:

1) Recall (reporting bias)
2) Contamination bias
3) Compliance/adherence bias
4) Lost to follow up bias

Observer-related

1) Interviewer (proficiency) bias
2) Diagnosis/surveillance (expectation) bias

Question 28

Define Recall (reporting) bias. Is it measurement bias or selection bias?

Answer 28

Measurement bias.
-a differential level of accuracy/detail in provided information between study groups

• exposed or diseased subjects may have greater sensitivity for recalling their history (better memory; easier to remember if more severe) or amplify (exaggerate) their responses
• Individuals can report their “effects” of exposure, disease symptoms or treatment differently b/c they are part of the study. This is called Hawthorne effect: Alteration of behavior by the subjects of a study due to their awareness of being observed

Question 29

Define Contamination bias. Is it measurement bias or selection bias?

Answer 29

Measurement bias.

-members of the control group accidentally, or outside of the study protocol, receive the treatment (or similar) or are exposed to the intervention being studied

Question 30

Define Compliance/adherence bias. Is it measurement bias or selection bias?

Answer 30

Measurement bias.

-Groups being interventionally studied have different compliances.

Question 31

Define Lost to Follow-up bias. Is it measurement bias or selection bias?

Answer 31

Measurement bias.

Groups being studied have different withdrawal or lost to follow up rates OR there are other differences between those that stay in the study and those that withdraw or are lost to follow up.
-Differential vs non differential

Question 32

Define Interviewer (proficiency) bias. Is it measurement bias or selection bias?

Answer 32

-A systematic difference in soliciting, recording, or interpreting on the part of the researcher (or their assistants)

Interviewers knowledge may influence the structure, or tone, of questions or followup questions which may influence response from the study subject OR,

Interventions/treatments are not applied equally between groups due to skill or training differences of study personnel or differences in study procedure compliance by staff at different sites
-can be conscious or unconscious actions of the interviewer

Question 33

Define Diagnosis/surveillance (expectation) bias. Is it measurement bias or selection bias?

Answer 33

Measurement bias.

Different evaluation, classification, diagnosis, or observation between study groups

observers may have preconceived expectations of what they should find in examination, evaluation, or follow up
-“Hawthorne-like effect” from the researchers’ perspective

Question 34

What is misclassification bias?

Answer 34

Error in picking out/classifying either disease or exposure status, or both for the patients

-it is a source of measurement (information/observation) bias

You may have TB but i place you in category that you don’t

Question 35

What are two types of misclassification bias?

Answer 35

Non-differential where the error in both groups are equal.

Differential where the error in one group differently than others

Question 36

Describe non-differential misclassification bias and its effect to your estimates of association

Answer 36

Misclassification of exposure or disease which is UNRELATED to the other (disease or exposure), spending on study design

EFFECT: for dichotomous (2 category) variables, bias can move the measure of association (RR/OR) TOWARDS 1.0; it attenuates (reduces) your effect estimates of association

Example: RR of 0.3 moves to 0.7. Attenuation towards 1.0
Example: OR of 1.0 moves to 1.2; attenuation towards 1.0
(both move closer to 1.0)

Question 37

Describe differential misclassification bias and its effect to your estimates of association

Answer 37

Misclassification of exposure or disease is RELATED to the other (disease or exposure), depending on the study design

EFFECT: bias can move the measure of association (RR/OR) IN EITHER DIRECTION IN RELATION TO 1.0; it can inflate or attenuate your effect estimates of association

Example: RR of 0.8 moves to 0.2; or; 1.4 moves to 2.1
-Inflation away from 1.0

Example: OR of 2.3 moves to 1.1 or 0.6 moves to 0.9
-attenuation towards 1.0

CAN move away from OR towards 1.0

Question 38

Name some controlling for biases

Answer 38

1) Select the most precise, accurate, and medically-appropatie measures of assessment and evaluation/observation
2) Blinding/masking
3) Us multiple sources to gather all information
4) Randomly allocate (distribute) observers/interviewers for data collection
5) Build in as many methods necessary to minimize loss to follow up