Observational Study Design

Question 1

descriptive studies

Answer 1

aim to describe occurrence and distribution of disease or other phenomena

descriptive stats

Question 2

analytic studies

Answer 2

aim to test hypothesis or provide explanation aout a disease or other phenomena

inferential stats

Question 3

case report

Answer 3

detailed presentation of the symptoms, signs, diagnosis, treatment, follow up of indiv pt

can contain demographic profile of the pt but usually unusual or novel occurrence

Question 4

case series

Answer 4

presentation of a disease in a number of pts

no control or comparison groups

Question 5

cohort study

Answer 5

cohort/group of subjects selected based on the exposure to a risk factor at the beginning of a study
-divide subjects into exposed vs non exposed
-selected from the same source population (no inherent confounding)

followed in time to determine which will dev the disease

not good for rare diseases bc time consuming, laborious, expensive

Question 6

cohort study calculations

Answer 6

1. absolute risk for each group (exposed vs non exposed)
2. difference b/t the two risks or relative risks b/t two groups

Question 7

inception cohort

Answer 7

pt’s just diagnosed then followed to determine prognosis (survival)

Question 8

historical cohort

Answer 8

aka retrospective

researcher has access to info about the prior exposure of a particular group/cohort to see which developed the disease of interest

still separated by exposure to risk at a time point in the past

Question 9

case control study

Answer 9

compare people who do have the diseases/cases with similar people who do not

start with outcome (subjects selected based on presence/absence of specific disease)

then look into past for exposures to a risk and examine frequency of exposure in cases vs controls

good for rare diseases, easy/cheap/quick

aka compare odds of exposure of risk with cases vs controls

Question 10

issues of case control

Answer 10

matching- attempt to ensure comparability and reduce the variabilty/systemic differences due to background variables not of interest

bias- selection bias, interview bias, completeness/accuracy of recorded info

selection of cases- explicitly defined criteria prior to selection, from variety of sources

selection of controls- cases and controls should stem from same population

Question 11

cross sectional studies

Answer 11

analyzes data collected from a pop or subset at a specific point in time
-examine exposure and outcome that occur at the same single time point

aka prevalence survey

Question 12

longitudinal study

Answer 12

repeated observations of same subjects over a period of time