Epidemiology Flashcards
(37 cards)
What are crossectional studies
This is a study of exposure of a section of a study population & outcome at one point in time or over a short period of time.
Types of cross sectional studies
Descriptive cross sectional studies; determines frequency & distribution of outcome (diseases and health related conditions) in a specified population.
Analytical cross-sectional studies;
study the association between exposure and outcome at the same time
Steps taken in a cross-sectional study
- The investigator identifies a study population in a specified study area/community
- Takes a cross-section of this population or community at a certain point in time
3.Then investigates the presence or absence of exposure and the outcome (disease) for each individual selected in a study sample.
4.Finally data analyzed to establish the association / relationship between the exposure and the outcome (disease).
Define a Survey
Is an observational cross-sectional study, which allows selection of a large sample of study participants from a population to be involved in a study to determine prevalence/frequency & associated factors
Types of surveys
1.Descriptive Cross-sectional surveys
2.Comparative cross-sectional surveys or Analytical surveys
Examples of surveys
1.National surveys;
National HIV/Malaria/Sickle cells disease survey
2.Health survey;
Uganda Demographic and Health Survey
3.Community survey;
A Safe male circumcision (SMC) survey in Kiteredde
Pros of cross sectional studies
1.Short duration
2.Cheap
3. Estimate Prevalence
4.Can set & prove hypothesis (analytical cross
sectional studies
Cons of cross sectional studies
1.Temporal association ( temporality) is weak
2.Recall bias
3.Can’t estimate incidence
4.Not suitable for describing natural history of a disease
Case control studies
Retrospective analytical study;
Identifies cases (diseased individuals) & identical controls (non-diseased) from the same study population, to study their level of exposure back in the time. Then determine the association btn Exposure & outcome (disease).
Types of case control studies that use odds ratio (OR)
Community or hospital based case- control study.
Types of studies that use Relative ratio (RR)
1) Prospective & Retrospective cohort study
2) Time Series study.
Distinguish between case-control studies and cohort studies
Case-control studies are retrospective and cohort studies are are both retrospective and prospective studies
Cohort studies
Longitudinal Analytical study;
Identifies two similar cohorts from a selected study population, one is exposed & the other unexposed, then observed overtime for a common outcome in the two cohorts. Then determine the association btn Exposure & outcome
Pros of case-control studies
1) Suitable for rare diseases
2) Cost effective in resource
3) Saves time
Cons of case-control studies
1) Susceptible to selection bias and Recall bias
2) Difficult to prove that exposure led to outcome
Pros of cohort studies
1) Study subjects selected before disease detection
2) Exposure status determined before outcome
3) can study multiple outcomes
4) Strong temporal association
5) suitable for Natural history of disease
6) No selection or recall bias
Cons of cohort studies
1) Time consuming
2) Expensive
3) Ineffective for rare diseases or those with long latency
4) Loss to follow up is common
Study designs in Interventional studies
*Lab. Experiments
*Animal Studies/Trials
*Randomised Control Trials (RCT) & Non-RCT
*Clinical Trials
*Community/Field Trials
Randomised control trials
*Scientific/medical experiment testing effectiveness of new treatment.
* Diseased patients are randomly selected into 2 or more groups & blindly exposed to different treatments (A – new treatment, B – Placebo), their response/ outcome observed and treatment efficacy assessed, and adverse effects reported
Methods of carrying out Randomised Control trails
1) Simple Randomization
2) Stratified Randomization
3) Systematic Randomization
4) Clustered Randomization
Define Blinding
Refers to Masking of information from one or more parties in a controlled trial regarding therapy to prevent performance or detection bias.
Discuss the types of blinding
1) Single blinding:
study participants/patients are blinded
2) Double blinding:
Research assistant/ clinician and participants/patients are blinded
3) Triple blinding:
Investigator/ Research assistant/ clinician/ Pharmacist , study participants/patients & data analyst are blinded.
Reasons for blinding
1) Prevent control bias
2) Prevent placeable bias
3) Control experiemental bias
What do you understand by clinical studies
A prospective biomedical or clinical study that assess new clinical interventions (novel vaccine, drug, diet/ nutritional supplement, or medical device) in comparison to Safety, Efficacy & Mode of Action (MOA) of known interventions.
