Observational Research Terms in this set (35) Incidence: The proportion of people who develop a given disease or condition within a specified time period Prevalence: The number of existing cases of a disease or condition at a given point in time ex

Observational Research Terms in this set (35) Incidence: The proportion of people who develop a given disease or condition within a specified time period Prevalence: The number of existing cases of a disease or condition at a given point in time expressed as a proportion of the total population at risk Primary Purposes of Observational Studies: 1. Descriptive: examining the distributions of predictors and outcomes in a population 2. Analytic: characterizing associations between these predictor and outcome variables What is a cross-sectional study? observations made on a single occasion with no follow up period - linked to prevalence What is a cohort study? observations made in a group of subjects that is followed over time - linked to incidence What are cross-sectional studies used for? to examine associations Cross-sectional studies are well suited for describing variables and their distribution parts, but why are they difficult to establish causality? Because they measure only prevalence, rather than incidence. Need to be cautious when drawing inferences about causes, prognosis, or natural history of a disease Cohort studies can be categorized into what two types? Prospective and Retrospective What is a prospective cohort study? Begin in the present, and follow subjects into the future Why would a prospective cohort study be better than a retrospective cohort study? allows investigators to measure variables more completely and accurately than is possible retrospectively What is a retrospective cohort study? examines information and specimens that have been collected in the past. What would be the steps in collecting a retrospective cohort study? 1. identify an existing cohort that has some predictor information already recorded 2. assess loss to follow up that has occurred 3. measure the outcome variables that have already occurred Observational Research What are some weaknesses to a retrospective cohort study? - limited control the investigator has (study already conducted, can't change the past) - existing data may be incomplete, inaccurate, or measured in not ideal ways to answer the research question Statistical method for expressing prevalence in cross-sectional studies # individuals with disease/condition at a given point in time / # individuals at risk Statistical method for expressing incidence in cohort studies # individuals who get a disease/condition / (# individuals at risk) x (time period at risk) What are the three measures of the statistical approach Risks, odds, and rates (same numerator) - estimates of frequency of a dichotomous outcome in subjects who have been followed for a period of time Cohort studies in a nut-shell: - sequence of measurements is the same as the chronology of cause and effect - predictor variables are measured first - outcomes are observed during follow up How does an investigator "work backwards" in a case-control study vs a cohort study? 1. choose sample of people who have the outcome of interest (cases) 2. choose sample of people without the outcome of interest (control) 3. compare levels of predictor variables between two samples and see which predictors are associated with the outcome What is the point of a case-control study? A case series of those with the disease can identify an obvious risk factor using prior knowledge of the prevalence of the risk factor in the general population Are case-control studies good for studying rare-diseases? Yes! Relatively efficient for studying rare diseases, and relatively inexpensive. - VS. Cohort and cross-sectional: expensive, require thousands of subjects to identify risk factors for a rare disease Why compare predictor variables in a case- control study? Looks backwards to find differences in predictor variables that may explain why the cases got the disease and for controls that did not What is a nested case-control study? A case-control study within a cohort study, compares incident cases nested in a cohort study with controls drawn at random from the rest of the cohort. - allows a random sample of the entire cohort to serve as the control for several different sets of cases What is the incidence-density nested case- control? allows the investigator to analyze risk relationships taking into account changes over time in the risk factor levels and loss to follow up What would a case-crossover variant of the case-control design be used for? It is useful for studying the short-term effects of intermittent exposures How to evaluate causality for case-control and cohort studies 1. must establish a time sequence that documents the exposure preceding the disease 2. look at the strength of the association using relative risk (unique to these designs) 3. the relationship should also have biologic credibility (should be able to pose some biological mechanism by which exposure might reasonably alter risk of developing disease) 4. show consistency with other studies 5. presence of a dose-response relationship provides evidence for causality What is Methodological research? Involves the development and testing of measuring instruments for use in research or clinical practice (decision rules) - used extensively in healthcare research--> use to establish the reliability and validity of clinical measurement tools - DOES NOT involve treatment effectiveness What is Outcomes-based research? Impetus for comprehensive methodological study of health status and functional assessment tools - emphasize the use of outcome instruments as a way of indicating quality of care and quality of life Observational Research What are the issues of reliability when measuring tools for research or clinical practice? - the rater - the tool itself How to support the accuracy of measurements taken in a clinical study? Intra-rater and Inter-rater reliability should be established - rater reliability is of primary importance The most comprehensive approach to methodological study is ___ developing a new tool - must start with a clear description of a problem for which a good measurement is not available Instruments are never absolutely ____ or _____ reliable or valid What is Historical Research? collecting information that exists on the record, including historic documents, personal papers, journals, official records, etc. to critically review in an effort to understand how and why past events occurred - used to anticipate future events - cause and effect statements cannot be made (only correlation) Historical research.... synthesizes what is already known into systematized accounts of the past and discuss potential relationships between variables based on sequencing of events and associated underlying characteristics of variables Use for historical research whenever possible primary sources - original documents - letters - videotapes - eyewitness accounts - direct recordings of events - photographs Secondary analysis: using existing databases to re-examine variables and answer questions other than those for which the data were collected -secondary sources: biographies, textbooks, literature reviews, newspaper accounts, etc