Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

INT > EPIDEMIOLOGICAL STUDIES; ANALYSIS OF CANCER RISK > Flashcards

EPIDEMIOLOGICAL STUDIES; ANALYSIS OF CANCER RISK Flashcards

1
Q

2 CATEGORIES OF EPIDEMIOLOGICAL STUDIES

A

EXPERIMENTAL (AIMAL EXPERIMENTS RCTs..)

OBSERVATIONAL ( COHORT, CASE CONTROL, CROSS SECTIONAL, GENE ENVIRONMENT, GENE-WIDE ASSOCIATION STUDY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

OTHER NAMES FOR COHORT STUDY

A
  • LONGITUDINAL STUDY
  • INCIDENCE STUDY
  • FORWARD LOOKING STUDY
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

FEATURES OF COHORT STUDIES

A
  • COHORTS ARE IDENTIFIED PRIOR TO APPEREANCE OF DISEASE UNDER INVESTIGATION (E.G. A GROUP THAT HAS A CERTAIN RISK FACTOR)
  • THE STUDY GROUPS ARE OBSERVED OVER A PERIOD OF TIME TO DETERMINE THE FREQUENCY OF DISEASE AMONG THEM
  • THE STUDY PROCEEDS FROM CAUSE TO EFFECTS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

INDICATIONS FOR DOING A COHORT STUDY

A
  • THERE IS GOOD EVIDENCE OF ASSOCIATION BETWEEN EXPOSURE AND DISEASE
  • EXPOSURE IS RARE
  • ATTRITION OF STUDY POPULATION CAN BE MINIMIZED
  • SUFFICIENT FUNDING IS AVAILABLE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

TYPES OF COHORT STUDIES

A
  • PROSPECTIVE (CLASSIC EXAMPLE, FOLLOW UP OF EXPOSED VS UNEXPOSED GROUPS TO MONITOR DISEASE DEVELOPMENT)
  • RETROSPECTIVE (OUTCOME HAS OCCURED BEFORE THE START OF THE INVESTIGATION, LOOKING BACK AT RECORDS, AKA HISTORICAL COHORT AND NONCURRENT COHORT)
  • AMBI-DIRECTIONAL (HAVE ELEMENTS OF BOTH PROSPECTIVE AND RETROSPECTIVE COHORT; THE COHORT IS IDENTIFIES FROM PAST RECORDS AND FOLLOWED UP PROSPECTIVELY INTO THE FUTURE FOR THE FURTHER ASSESSMENT OF OUTCOME)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

DISADVANTAGES OF COHORT STUDIES

A
  • MIGHT TAKE A LONG TIME
  • REQUIRE A SUFFICIENT AMOUNT OF FUNDING FOR A LONG PERIOD
  • MISSING OF STUDY SUBJECTS
  • NOT SUITABLE FOR RARE DISEASES
  • LARGE POPULATION NEEDED
  • STUDY ITSELF MIGHT ALTER PEOPLE’S BEHAVIOURS
  • EXTENSIVE RECORD KEEPING
  • PROBLEM OF ATTRITION OF INITIAL COHORT IS COMMON
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

OUTPUTS OF COHORT STUDIES

A 
RELATIVE RISK (INCIDENCE RISK AMONG EXPOSED/INCIDENCE RISK AMONG UNEXPOSED) --> ESTIMATES THE MAGNITUDE OF ASSOCIATION BETWEEN AN EXPOSURE AND DISEASE
incidence risk = number of people who develop a condition/ total number of exposed people (or unexposed)

ATTRIBUTABLE RISK (INCIDENCE RISK AMONG AN EXPOSED GROUP - INCIDENCE RISK AMONG A NON-EXPOSED GROUP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

BIASES IN COHORT STUDIES

A
  • DIFFERENTIAL LOSS OF FOLLOW UP
  • CONTAMINATION
  • SELECTION BIAS
  • INFORMATION BIAS
  • MISCLASSIFICATION BIAS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

OTHER NAMES FOR CASE CONTROL STUDIES

A
  • CASE COMPARISON STUDY
  • CASE COMPEER STUDY
  • CASE HISTORY STUDY
  • CASE REFERENT STUDY
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

FEATURES OF CASE CONTROL STUDIES

A
  • BOTH EXPOSURE AND OUTCOME HAVE OCCURED BEFORE THE START OF THE STUDY
  • THE STUDY PROCEEDS BACKWARDS FROM THE EFFECT TO CAUSE
  • IT USES A CONTROL OR COMPARISON GROUP TO SUPPORT OR REFUTE AN INFERENCE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

CASE CONTROL VS COHORT STUDIES

A

CASE CONTROL STARTS WITH DISEASES AND NOT DISEASES, WHILE COHORT STARTS WITH EXPOSED AND UNEXPOSED

CASE CONTROL DETERMINES IF 2 GROUPS DIFFER IN EXPOSURES WHILE IN COHORT STUDIES FOLLOW UP IS DONE TO DETERMINE DIFFERENCE IN RATES AT WHICH DISEASE DEVELOPS IN RELATION TO EXPOSURE

DIFFERENT OUTPUTS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

HOW ARE CONTROLS IN CASE CONTROL STUDIES SELECTED?

A
  • COMPARABILITY MORE IMPORTANT THAN REPRESENTATIVENESS
  • THE CONTROL SHOULD BE AT RISK OF THE DISEASE
  • THE CONTROL SHOULD RESEMBLE THE CASE IN ALL RESPECTES EXCEPT FOR THE PRESENCE OF THE DISEASE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

SOURCES OF CASES AND CONTROLS FOR CASE CONTROL STUDIES

A

HOSPITAL BASED (EASIY RECRUITMENT AND COOPERATION BUT POPULATION WITH MORE RISK FACTORS FOR DISEASES, DOESN’T RESEMBLE GEN POP)

POPULATION BASED (MOST REPRESENTATIVE OF GEN POP!!!!!!!!!!!!, USUALLY HEALTHY, REQUIRES MORE TIME, MONEY AND ENERGY, EXPOSURES TO RISK FACTORS MIGHT BE VERY DIFFERENT)

NEIGHBOURHOOD CONTROLS/TELEPHONE EXCHANG RANDOM DIALLIG (CONTROL AND CASES SIMILAR IN RESIDENCE, EASIER THAN SAMPLING THE POPULATION, BUT LACK OF CO-OPERATION, SECURITY ISSUES, NOT REPRESENTATIV OF GEN POP)

BEST FRIEND CONTROL/SIBLING CONTROL (ACCESSIBLE, COOPERATIVE, OFTEN SIMILAR TO CASES, BUT COULD LEAD TO OVERMATCHING)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

BIASES IN CASE CONTROL STUDIES

A
  • SELECTION BIAS
  • INFORMATION BIAS
  • CONFOUNDING BIAS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

OUTPUT OF CASE CONTROL STUDIES

A 
ODDS RATIO (RATIO OF THE ODDS THAT THE CASES WERE EXPOSED TO THE ODDS THAT THE CONTROLS WERE EXPOSED)
Odds: the ratio of the number of ways an event can occur to the number of ways an event cannot occur
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

ADVANTAGES OF CASE CONTROL STUDIES

A
  • ONLY REALISTIC STUDY DESIGN FOR UNCOVERING AETIOLOGY IN RARE DISEASES
  • IMPORTANT IN UNDERSTANDING NEW DISEASES
  • COMMONLY USED IN OUTBREAKS INVESTIGATION
  • USEFUL IF INDUCING PERIOD IS LONG
  • RELATIVELY INEXPENSIVE
17
Q

DISADVANTAGES OF CASE CONTROL STUDIES

A
  • SUSCEPTIBLE TO BIAS IF NOT CAREFULLY DESIGNED
  • ESPECIALLY SUSCEPTIBLE TO EXPOSURE MISCLASSIFICATION
  • ESPECIALLY SUSCEPTIBLE TO RECALL BIAS
  • RESTRICTED TO SINGLE OUTCOME
  • INCIDENCE RATES NOT USUALLY CALCULATED
  • CANNOT ASSESS EFFECTS OF MATCHING VARIABLES
18
Q

OTHER NAME FOR CROSS SECTIONAL STUDIES

A

PREVALENCE STUDIES

19
Q

WHAT ARE CROSS SECTIONAL STUDIES?

A
  • SINGLE EXAMINATION OF POPULATION (WHOLE OR A SAMPLE) AT ONE POINT IN TIME
  • MEASURE EXPOSURE AND EFFECT SIMULTANEOUSLY
20
Q

TYPES OF CROSS SECTIONAL STUDIES

A
  • POINT PREVALENCE OR PERIOD PREVALENCE
  • DESCRIPTIVE (DESCRIBE PRESENCE OF DISEASE, DISABILITY AND SYMPTOMS, DIMENSIONS OF POSITIVE HEALTH, ATTRIBUTES RELATED TO HEALTH) OR ANALYTICAL CROSS-SECTIONAL (STRENGTH OF ASSOCIATION BETWEEN DISEASE AND RISK FACTORS, DETERMINNTS OF DISEASE/CONDITIONS, PREDICTORS OF DISEASE)
21
Q

ADVANTAGES OF CROSS SECTIONAL STUDIES

A
  • PROVIDE ESTIMATE OF THE DISEASE BURDEN (PREVALENCE)
  • RELATIVELY SHORT DURATIO
  • EASY AND QUICK
  • LESS COSTLY
  • USEFUL FOR CHRONIC CONDITIONS WITH LOW CASE FATALITY
  • STARTING POINT FOR COHORT STUDIES FOR SCREENING EXISTING DISEASS
  • PROVIDE WEALTH OF DATA FOR FURTHER RESEARCH
  • ALLOW A RISK STATEMENT, ALTHOUGH THESE ARE NOT PRECISE
22
Q

DISADVANTAGES OF CROSS SECTIONAL STUDIES

A
  • DOESN’T PROVIDE ESTIMATE OF DISEASE OCCURENCE
  • NO DIRECT ESTIMATE OF RISK POSSIBLE
  • RARE DISEASES, SHORT DURATION, HIGH FATALITY NOT DETECTED
  • NATURAL HISTORY OF DISEASE INFO IS MINMAL
  • PRONE FOR BIASES FROM SELECTIVE SURVIVAL
  • NOT POSSIBLE TO ESTABLISH TEMPORALITY
  • WEAK DESIGN FOR PROVING CAUSALITY
23
Q

3 MAJOR TYPES OF OBSERVATIONAL STUDIES

A
  • COHORT
  • CASE CONTROL
  • CROSS SECTIONAL
24
Q

WHAT IS THE GENE-ENVIRONMENT INTERACTION STUDY?

A

THE DIFFERENTIAL OF THE GENOTYPE RESPONSE IN CONNECTION WITH THE ENIRONMENTAL VARIATION

25
Q

HOW MANY MODELS OF GENE-ENVIRONEMTN INTERACTION HAV BEEN PROPOSED AND WHAT ARE THEY?

A

5

MODEL A: THE EFFECT OF THE GENOTYPE IS TO PRODUCE, OR INCREASE EXPRESSION OF, A ‘RISK FACTOR’ THAT CAN ALSO BE PRODUCED NONGENETICALLY

MODEL B: THE GENOTYPE EXACERBATES THE EFFECT OF THE RISK FACTOR, BUT THERE IS NO EFFECT OF THE GENOTYPE IN UNEXPOSED PERSONS

MODEL C: THE EXPOSURE EXACERBATES THE EFFECT OF THE GENOTYPE, BUT THERE IS NO EFFECT OF THE EXPOSURE IN PERSONS WITH THE LOW RISK GENOTYPE

MODEL D: BOTH THE EXPOSURE AND THE GENOTYPE ARE RECQUIRED TO INCREASE RISK

MODEL E: THE EXPOSURE AND THE GENOTYPE BOTH HAVE SOME EFFECT ON DISEASE RISK, AND WHEN THEY OCCUR TOGETHER RISK IS HIGHER OR LOWER THAN WHEN THEY OCCUR ALONE (NO INTERACTION BETWEEN THEM)

26
Q

METHODS OF ANALYSIS OF GENE-ENVIRONMENT INTERACTION STUDIES - TRADITIONAL GENETIC DESIGNS

A
  • ADOPTION STUDIES
  • TWIN STUDIES (MONOZYGOTIC TWINS)
  • FAMILY STUDIES (COMPARISON OF LOW RISK CONTROLS TO HIGH RISK CHILDREN TO DETERMINE THE ENVIRONMENTAL EFFECT ON SUBJECTS WITH DIFFERENT LEVELS OF GENETIC RISK)
27
Q

METHODS OF ANALYSIS OF GENE-ENVIRONMENT INTERACTION STUDIES - MOLECULAR ANALYSES

A
  • INTERACTION WITH SINGLE GENES (SNPs)
  • INTERACTION WITH MULTIPLE GENES (POLYGENIC APPROACH, SINCE ONE EXTERNAL FACTOR COULD INTERACT WITH MULTIPLE GENES)
  • GENOME WIDE INTERACTIO STUDIES (GENOME WIDE INTERACTION SCAN - GEWIS - APPROACH EXAMINES THE INTERACTION BETWEEN THE ENVIRONMENT AND A LARGE NUMBER OF INDEPENDENT SNPs)
28
Q

ADVANTAGES OF GENE-ENVIRONMENT INTERACTION STUDIES

A
  • IMPORTANT IMPLICATIONS FOR PUBLIC HEALTH

- AIDS IN PREDICTING DISEASE RATES AND PROVIDES A BASIS FOR WELL-INFORMED RECOMMNDATIONS FOR DISEASE PREVENTION

29
Q

DISADVANTAGES OF GENE-ENVIRONMENT INTERACTION STUDIES

A
  • LACK OF REPLICATION (REPRODUCIBILITY)

- ADDITIVE VS MULTIPLICATIVE MODEL (HOW DO ENVIRONMENT AND GENES INTERACT EXACTLY)

30
Q

WHAT IS GENOMIC WIDE ASSOCIATION STUDY?

A

AN APPROACH THAT INVOLVES SCANNING BIOMARKERS SUCH AS SINGLE NUCLEOTIDE POLYMORPHISM, or SNPs, FROM DNA OF MANY PEOPLE, IN ORDER TO FIND GENETIC VARIATION, ASSOCIATED WITH A PARTICULAR DISEASE FIELD PHENOTYPES

31
Q

BASIC PURPOSE OF GENOME WIDE ASSOCIATION STUDIES

A

TO DETERMINE IF EITHER ALLELE AT A GIVEN SNP IS OVERREPRESENTED IN EITHER CASES OR CONTROLS

CASES: INDIVIDUALS WITH A DISEASE OF INTERETS, CONTROLS: INDIVIDUALS WITHOUT THE DISEASE

—> SNPs THAT SHOW A STRONGER ASSOCIATION THAN EXPECTED BY CHANCE ARE REGARDED AS MARKERS OF CANDIDATE GENES

32
Q

STEPS IN GENOME WIDE ASSOCIATION STUDIES

A
  • GATHER SAMPLE (USUALLY AT LEAST 1000 OF BOTH CASES AND CONTROLS)
  • DNA SAMPLE
  • HYBRIDIZE DNA TO THE ARRAY
  • IDENTIFY (‘CALL’) GENOTYPES
  • IMPUTE ADDITIONAL SNPs
  • PERFORM STATISTICAL ANALYSIS
  • INTERPRET FINDINGS

FOR EACH SNP: COMPUTE FREQUENCY ON CASES AND CONTROL, COMPUTE ODDS RATIO, COMPUTE P VALUE OF THE ODDS RATIO

33
Q

WHAT STATISTICAL TRESHOLD NEEDS TO BE EXCEEDED TO CONCLUDE A SNP CONTRIBUTES TO A TRAIT?

A

5x10^-8

34
Q

BONFERRONI CORRECTIONS

A

a multiple-comparison correction used when several dependent or independent statistical tests are being performed simultaneously

(THE ORIGINAL P VALUE IS DIVIDED BY THE NUMBER OF TESTS PERFORMED TO GET THE ACTUAL NUMBER REQUIRED FOR STATISTICAL SIGNIFICANCE, USED IN E.G. GENOME WIDE ASSOCIATION STUDIES WHEN THOUSANDS OF SNPs ARE INVESTIGATED)

35
Q

ADVANTAGES OF GWAS?

A
  • VERY SUCCESSFUL IN IDENTIFYING NOVEL VARIANT-TRAIT ASSOCIATIONS
  • CAN LEAD TO DISCOVERY OF NOVEL BIOLOGICAL MECHANISMS
    TRANSLATING BIOLOGICAL INSIGHTS INTO MEDICAL ADVANCEMENTS
  • CAN PROVIDE INSIGHT INTO ETHNIC VARIATION OF COMPLEX TRAITS
  • RELEVANT TO THE STUDY OF LOW FREQUENCY AND RARE VARIANTS
  • CAN BE USED TO IDENTIFY NOVEL MONOGENIC AND OLIGOGENIC DISEASE GENES
  • DATA ARE EASILY SHARED, AND PUBLICLY AVAILABLE DATA FACILITATES NOVEL DISCOVERIES
36
Q

DISADVANTAGES OF GWAS?

A
  • PENALISED BY AN IMPORTANT MULTIPLE TESTING BURDEN
  • EXPLAIN ONLY A MODEST FRACTION OF THE MISSING HERITABILITY
  • DO NOT NECESSARILY PINPOINT CAUSAL VARIANTS AND GENES
  • CANNOT IDENTIFY ALL GENETIC DETERMINANTS OF COMPLEX TRAITS
  • HAVE LIMITED CLINICAL PREDICTIVE VALUE
  • SIGNALS MAY BE DUE TO CRYPTIC POPULATION STRATIFICATION

INT (52 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions