Analytical study Flashcards
ANALYTICAL STUDIES
• Measure ______ and ______ on populations based on hypothesis generated during previous descriptive studies
• Determine the existence and strength of association between _________________________ and the _____________ in question
Cause and effect
suspected risk or etiological factor and the
disease
Analytical Studies
• Have _________ or __________ group(s) which must be similar to cases in all aspect except for the __________________________
control or comparison
outcome or disease under study
Analytical studies
• Include ____________ study, ________ study.
case-control
cohort
Basic Questions in Descriptive & Analytical studies
•Descriptive studies ask the questions
_____,______,_________ ?
•Analytical studies in addition asks _______?
who, when and where
why
Case-Control Study
• An _________ ,__________ study in which comparisons are made between _________________ and ____________________
observational, analytical
individuals who have the disease (cases)
individuals who do not (controls)
Case-Control Study
• Is a _____________ study; goes _____wards in time from ________ to _________
retrospective; back
effect (disease) to cause
Case-Control Study
• Compares the _________ of previous exposure to the suspected etiological factor in persons with the disease
(cases) and those without the disease (controls)
frequency
Case control study
Steps in conducting a case control study
1. —————— of ——— and ——-
2. ———-
3. Measurement of ———-
4. Analysis and interpretation
- Selection of cases and control
- Matching
- Measurement of exposure
- Analysis and interpretation
Selection of cases and control
• A case is first of all defined by means of ___________
• Cases must belong to same ________ and ___________ group
• Eligibility criteria must be adhere to
• Cases are obtained from hospital records, , death certificate, employer records and the general population
• Information about cases can be gathered from cases
themselves, relatives and friends or from records.
diagnostic criteria
clinical and histological
Selection of control
• The control must be _____________ under study
• Should resemble the cases in ______________
• The control must (be or not be?) exposed to the suspected causative factor of
the disease under study.
free of the disease
other characteristics
Not be
Which is easier?
Selecting cases or selecting controls
Selecting cases
Hospital control
• Hospital control are more likely to have similar characteristics as the study group in terms of their ______________ and ______________ factors
• They tend to be (more or less?) exposed to the risk factors of disease than the general population
• They may differ from the ______________ population
• They are easily identified and are almost always available for interview and tend to be cooperative
catchment area and socioeconomic
More
normal healthy
Relatives and friends
• Relative as well as friends of cases under study (may or may not?) be used as control
• Siblings (must or must not?) be used when studying genetic condition
• The disadvantage is that they may be __________ in terms of __________ and other characteristics
May
Must not
too similar; exposure
Neighbours
• Selected from persons living in the same area, working in the same
place, or attending the same school with the cases
Okay
General population
• Population control have the advantage of using ____________ that represent well the population of the area
• They are usually selected by means of __________ sampling
• In developed world, ________________ can be randomly selected
healthy people
random
telephone number
Matching
• Matching is the process of selecting controls in such a way that they
are ______________ with regards to certain pertinent variables e.g. sex, race, occupation, socio-economic status and educational status
• These factors influence the outcome of disease
similar to cases
Measurement of exposure
• Information about exposure is obtained in a (similar or dissimilar?) way among the
cases and control.
• This may be done by means of interview, questionnaires, focus group discussion , check lists and studying past records such as hospital and employment records
similar
Analysis and interpretation
The Odds ratio is an estimate of the _____________.
It is known as ________________ ratio
It is a measure of __________________ between __________ and —————— .
relative risk
cross production
strength of association
risk factor and outcome
Odds ratio= _____/____
Where each letter stands for ?
ad/bc
a = number of exposed individuals who eventually
developed the disease
b= number of exposed individuals who did not develop
the disease
c=number of unexposed individuals who subsequently
develop the disease
d= number of un exposed individuals who did not
develop the disease
Odds Ratio
• OR=___________________________ x ___________________________/___________________________ x ___________________________ (ad/bc)
Exposed persons with the disease
unexposed without the disease
Exposed without the disease
unexposed with disease (ad/bc)
Odds Ratio
• Is a ratio of the odds that _________________________ to the odds that a ___________________
a case was exposed to the risk factor
control was exposed to the risk factor
Odds ratio
• Referred to as _____________ Ratio; ______________ , _______________
Cross Product
Relative Odds
Estimated Relative Risk
Advantages of Case-Control study
-Relatively _____,______,____________
-Suitable for studying _____-
diseases
-________ problems is minimal
-Require ____ sample size
measurement
easy, quick, inexpensive
rare; Ethical
small
Disadvantages of Case-Control Study
-________ bias; also information may be _________ or __________
-Bias in _________________________
-Can not measure _________
-Can not give accurate _______
Recall; missing or unavailable
selection of control group
incidence; risk
COHORT STUDY
• Type of analytical /observational study.
• Determines if there is an association between ______________ and ________________
• Also called _________ study, _________ study, _________ study.
a suspected cause( exposure) and
disease
prospective; incidence ; forward looking
COHORT STUDY
• The study proceeds from ______ to _________
cause to effect
cohort
• A group of people who share a ___________________________
within a _____________ period. e.g age( _______ cohort), class mates ( _______
cohort), exposure to infection within a defined period ( __________ cohort)
common characteristic or experience
defined time ; birth; class; exposure
• Cohorts are identified (prior to or after?) appearance of disease/outcome under
study and followed up.
prior to
Cohort study
• Begin with _______ groups (cohorts) – _________ and ___________ groups that have similar composition except for ______________________
• follow up both groups to see how many people in both groups develop disease/outcome under investigation
• May require long period of follow up
• Some participants lost to follow up (attrition)
two
exposed and unexposed
exposure to suspected etiology
Analysis of COHORT
• Quantification of association between suspected agent and disease
being investigated
• Record frequency of disease occurrence in both groups in two by two
table- ______________
• Calculate relative risk, attributable risk and make conclusion on cause
– effect relationship
incidence
Association between smoking and stroke
• Incidence in exposed=
______________ /___________ = ____/________
• Incidence in unexposed= ________________ /____________= _____ / ______
• Incidence in exposed=
Num of cases/num exposed
A /A+B
• Incidence in unexposed=
Num of cases/num not exposed
C / C+D
Relative Risk (RR)
• RR does not necessarily imply ___________ as it does not ___________________________
• Also called _____ Ratio or __________ Ratio
causal association
quantify the extent of disease causation by the risk factor
Risk; Morbidity
Analysis -
1.Relative risk
• Relative risk – relates the ____________________________ to ____________________________
incidence rate in the exposed
incidence rate in the unexposed
Analysis -
1.Relative risk
• RR =______________ / _____________
• If RR >1 _______________________
• If RR = 1 __________________________
• If RR < 1 ____________________
incidence in exposed
incidence in unexposed
risk of acquiring the disease is higher in those who are exposed
whether exposed or not risk is same
- Attributable risk
• _______________________________
•_______ risk in those who are exposed
• The amount of risk which can be ascribed to _________
Incidence rate in the exposed minus incidence rate in unexposed
Excess; exposure
• Attributable risk = ____________________________________________ =
__________________
Incidence in exposed – Incidence in unexposed
risk difference
Relative risk & attributable risk
• Relative risk measures __________________.
• Attributable risk measures the impact that _____________________ may have on the _______________
strength of association
removal of a certain factor
incidence of a disease
The higher the relative risk the ___________ the association of factor to disease.
high relative risk suggests _________
greater
etiology
Advantages of cohort studies
• Can determine ____________ of disease in exposed and unexposed
• No problem of _______ bias
• Can measure ______________
• Can test multiple effects of cause
incidence; recall
relative risk
Disadvantages of cohort studies
• Need ______ sample
• ________
• Time consuming
• Difficulty in ____________ of people - attrition
large
Expensive
follow up
