Which is the study design of choice for finding out circadian variation of fat content in expressed breast milk of mother of preterm babies:-
Ans. (a) Prospective CohortRef: Parks Text book of Preventive and Social Medicine 24th Ed; Page No-39Study design (Cohort)Study designBaselineFollow-upProspective CohortAssessed at the time of start of studyIn future dateRetrospective CohortAssessed at some time in past using historical data or cohortsIn present date (the outcome has already occurred)Ambispective CohortAssessed at some time in past using historical data or cohortsIn future date (not that the outcome may have occurred in some, but final assessment is done in a future date)Difference between case control study and cohort studyCase control studyCohort studyCommences from "effect to cause. Exposure and outcome occurred before start of investigation.Commences from cause to effect. Cohorts are if identified prior to appearance of the disease (or outcome) under investigation.We look for it suspected cause occur more often in those with the disease than among those without the disease.We look for if the disease occurs more frequently in those exposed, than in those not exposed.No attritionAttrition is a major problem.Quick results and relatively easy to carry outTakes long timeInvolves fewer subjectsInvolves large number of subjectsSuited for study of rare diseaseSuited for study of rare exposuresCheaperCostlyNo follow up is neededFollow up is an integral partOdds ratio obtainedIncidence rate, RR and AR, PAR are obtained.We get information on several etiological agent or risk factors.We get information on more than one disease outcome from single etiological agent.1st approach to testing a casual hypothesisUsed to test precisely formulated hypothesisRecall bias, section bias in an issueNo recall biasCross sectional test:* In single examination of a cross-section of population at one point of time.* Unit of study is the individual* More useful for chronic disease* It does not involve a follow up, hence is also known as cross- sectional study or snapshot of the population.* May not be a good measure to assess risk factors for disease which are acute in nature or fatal.* This study helps us in estimating the total number of present cases (or the prevalence of the disease).* The study includes survey of the population, or sample of the total population.
Prospective Cohort
Ambispective Cohort
Case control
Cross sectional
Epidemiology