Overview Observational studies are studies in which subjects are observed for the effect of exposures on outcomes without intervention by researchers Often done when randomization is not possible for logistical or ethical reasons Descriptive Studies Case report detailed description of a patient's symptoms, signs, treatment, and disease course conducted for hypothesis generation or to raise awareness of emerging diseases, rare pathologies or unusual presentations not useful for hypothesis testing Case series a group of case reports of patients with a similar exposure, treatment, or disease no comparison group not useful for hypothesis testin Prospective and Retrospective Studies Prospective studies patients enrolled before data collection participants followed over time data collected on exposures and outcomes as they arise Retrospective studies involve collecting historical information from a sample of patients enrollment occurs after exposure and outcome have already occurred Case-Control Study Retrospective (almost always) Compares patients with and without disease to asses their odds of a certain exposure Odds ratio (OR) is measure of disease association OR = odds of exposure among cases/odds of exposure in non-cases = ad/bc odds of exposure among cases = # cases with exposure/# cases without exposure = a/c odds of exposure among non-cases = # non-cases with exposure/# non-cases without exposure = b/d "How much more likely is it that patients with cirrhosis have been exposed to heavy alcohol use compared to controls?" Cohort Study Can be either prospective or retrospective Compares groups with and without an exposure to assess associations with subsequent disease Relative risk (RR) is measure of disease association RR = incidence rate in exposed group/incidence rate in unexposed group = [a/(a+b)]/[c/(c+d)] incidence rate in exposed group = # of exposed cases/(# total exposed cases and non-cases) = a/(a+b) incidence rate in unexposed group = # of unexposed cases/(# total unexposed cases and non-cases) = c/(c+d) "How much more likely are patients to develop cirrhosis if they are exposed to heavy alcohol use?" Cross-Sectional Study Exposure and outcome are assessed simultaneously Ascertains association not causality best used for gathering information and generating further hypotheses Prevalence is measure of disease association "How much higher is the proportion of cirrhosis patients with heavy alcohol use compared to those without cirrhosis?" Ecological Study Exposure and outcome assessed at the population level population defined geographically or temporally Prevalence and incidence are measures of disease association Often used for rapid hypothesis generation "How much higher is the proportion of cirrhosis patients in a country where average alcohol use is high compared to a country in which alcohol is illegal and of low use?" Disadvantage is the potential for "ecological fallacy" making spurious risk associations between populations which may not represent true risk association at the individual level e.g. assuming that people who live in a country with high alcohol use rates must be more likely to get cirrhosis by virtue of living in that country Sibling Studies Measures relative influence of environment vs genetics on trait variation Twin concordance study compares how often monozygotic and dizygotic twins both have the same trait or disease Adoption study 2 designs examines differences and similarities between child and adoptive vs birth parents examines differences and similarities between siblings raised by adoptive vs birth parents
QUESTIONS 1 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.ST.15.20) A recent study attempted to analyze whether increased "patient satisfaction" driven healthcare resulted in increased hospitalization. In this hospital, several of the wards adopted new aspects of "patient satisfaction" driven healthcare, whereas the remainder of the hospital continued to use existing protocols. Baseline population characteristics and demographics were collected at the start of the study. At the end of the following year, hospital use was assessed and compared between the two groups. Which of the following best describes this type of study? QID: 102599 Type & Select Correct Answer 1 Retrospective cohort 16% (30/188) 2 Prospective cohort 41% (77/188) 3 Retrospective case-control 13% (25/188) 4 Prospective case-control 13% (25/188) 5 Cross-sectional study 10% (19/188) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (M1.ST.15.18) A researcher interested in the relationship between vaccination and autism sends a survey to parents of children who are active patients at a large primary care practice. The survey asks several questions, including whether their children received their childhood vaccines on-time, and whether their children currently have a diagnosis of an autism spectrum disorder. Which of the following correctly identifies the study design used by the researcher? QID: 104024 Type & Select Correct Answer 1 Cross-sectional 55% (49/89) 2 Case-crossover 4% (4/89) 3 Cohort 18% (16/89) 4 Randomized controlled trial 2% (2/89) 5 Case-control 12% (11/89) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.ST.14.10) You would like to conduct a study investigating potential risk factors that predispose patients to develop cirrhosis. Using a registry of admitted patients over the last 10 years at your local hospital, you isolate all patients who have been diagnosed with cirrhosis. Subsequently, you contact this group of patients, asking them to complete a survey assessing their prior exposure to alcohol use, intravenous drug abuse, blood transfusions, personal history of cancer, and other medical comorbidities. An identical survey is given to an equal number of patients in the registry who do not carry a prior diagnosis of cirrhosis. Which of the following best describes the type of study you are attempting to conduct? QID: 104016 Type & Select Correct Answer 1 Cohort study 4% (2/52) 2 Meta-analysis 0% (0/52) 3 Case-control study 69% (36/52) 4 Cross-sectional study 13% (7/52) 5 Randomized controlled trial 0% (0/52) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (M1.ST.14.13) A new study shows a significant association between patients with a BMI >40 and a diagnosis of diabetes (odds ratio: 7.37; 95% CI 6.39-8.50) compared to non-diabetic patients. Which of the following hypothetical studies most likely yielded these results. QID: 103975 Type & Select Correct Answer 1 A study consisting of 1000 non-diabetic subjects; 500 patients with a BMI > 40 and 500 patients with normal BMI, followed for diagnosis of diabetes over their life time 17% (11/63) 2 A study consisting of 500 patients with diabetes and 500 patients without diabetes comparing BMI of subjects in both groups 48% (30/63) 3 A study consisting of 1000 genetically similar mice; 500 randomized to diet to maintain normal weight and 500 randomized to high caloric intake with the outcome of diabetes rates in both groups after 1 year 3% (2/63) 4 A study of 1000 patients with BMI > 40 with diabetes; 500 randomized to inpatient diet and exercise with goal BMI <25, and 500 randomized to no treatment with an outcome of glycemic control without medication after 1 year 3% (2/63) 5 A study of 1000 patients comparing rates of diabetes diagnoses and BMIs of diabetic and non-diabetic patients 16% (10/63) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK
All Videos (0) Stats | Observational Studies Stats - Observational Studies Listen Now 23:34 min 5/16/2021 32 plays 0.0 (0)