Prospective and Retrospective Studies

Which of the following is a limitation of case-control studies? A) Provide indirect estimate of risk via the odds ratio B) Representativeness of cases and controls often unknown C) Potential for considerable bias D) Timing of exposure-disease relationship difficult to determine E) All the above

E) All the above

Which of the following is an advantage to prospective cohort studies? A) Direct measures of the environment can be made. B) Enable the investigator to collect data on exposures and it's the most direct and specific test of the study hypothesis. C) The size of the cohort is under greater control by the investigators. D) Biological and physiological assays can be performed with decreased concern that the outcome will be affected by the underlying disease process. E) All the above

E) All the above

Which of the following is not true of cohort studies? A) Can be thought of as going from cause to effect. B) Allow for the calculation of incidence rates. C) Start with a group of subjects who lack a positive history of the outcome of interest and are at risk for the outcome. D) Include at least two observation points: one to determine exposure status and eligibility and a second (or more) to determine the number of incident cases. E) Involve the collection of secondary data.

E) Involve the collection of secondary data. (involves the collection of primary data)

A (Positive/Placebo) control design is used to justify uncertainty regarding whether the standard therapy helps and a (Positive/Placebo) control design is used to compare the new drug directly to the standard therapy

Placebo; Positive (positive control design is used when the standard therapy is known to be effective)

(Prospective/Retrospective) study designs are planned to follow a group of people over a period of time as seen in the Framingham study

Prospective

In (RCT's/cohort) designs the exposure is assigned to some and not others while in (RCT's/cohort) designs exposure is not assigned

RCT's; cohort

(Prospective/Retrospective) study designs are done after the fact making it an inferior design

Retrospective

A(n) (cumulative-incidence/incidence-density) design is a/w all cases of a disease selected during defined period of time, similar controls selected based on disease absence at end of defined time period, and fixed population

cumulative-incidence

A (single/double/triple)-blind design is when neither the subject nor experimenter is aware of group assignment.

double

An (population/exposure)-based cohort is made up of subjects with a common exposure, for example, workers exposed to lead during battery production.

exposure (other examples include occupation cohort, geographic cohorts, health care cohorts such as DM pts)

A(n) (population/exposure)-based cohort overcomes the limitations of (population/exposure)-based cohorts because they are more efficient at examining rare exposures such as occupational groups, may have higher exposures than the general population to specific hazards.

exposure; population

T/F: Community interventions are the gold standard of evidence in regard to intervention studies

false (randomized clinical trials are the gold standard)

T/F: In a prospective cohort study a significant amount of follow-up may be accrued in a relatively short period of time and the amount of exposure data collected can be quite extensive and available to the investigator at minimal cost.

false (should be retrospective -- these are the advantages of retrospective studies)

T/F: The honolulu heart program and the nurses' health study are examples of RCT's

false (they were major cohort studies -- gathered data through mailed questionnaires, interview and clinical exams)

T/F: In situations where you cannot do a blinded study such as surgery as an intervention or treatments with different durations of therapy you should select subjective outcomes to measure in order to reduce bias

false (you should select OBJECTIVE things like death, major complications, serious adverse events, etc -- can also conduct a triple blinded review of outcomes)

A(n) (cumulative-incidence/incidence-density) design is a/w new incident cases selected for study inclusion up to target case number, similar controls selected at time of case selection, and no pre-defined time period

incidence-density

An odds ration (greater/less) than 1 suggests it's a protective factor

less

(Population/Exposure)-based Cohort studies includes either an entire population or a representative sample of the population as seen in the Framingham study which used a random sample of 6,500 from targeted age range of 30 to 59 years.

population

Temporality, measurement bias/error, information bias, selection bias, and confound are all issues a/w (prospective/retrospective) designs

retrospective

A (prospective/retrospective) cohort study makes use of historical data to determine exposure level at some baseline in the past and is beneficial when you want a quick and cheap rough answer to a question

retrospective (need to trade off between a retrospective study design with the benefits of more immediate follow-up time and collection of primary exposure data in a prospective cohort design)

A (single/double/triple)-blind design is when the subject is unaware of group assignment.

single

A (single/double/triple)-blind design is when you conduct blinded review of outcomes by blinding the people analyzing the data

triple

T/F: An odds ratio is an estimated risk that may provide a good approximation of risk when controls are representative of the population of all controls, cases are representative of all cases and the frequency of disease in the population is small (Prevalence < 5%)

true

T/F: Case-control studies have potential for considerable bias d/t measurement of exposure status and selection of subjects

true

T/F: In cohort designs you can't ensure confounding variables are equally distributed and can't be 100% sure that some unmeasured factor is responsible for both exposure and outcome

true

T/F: It would be appropriate to do a case control study when exposure data are difficult/expensive to obtain prospectively, disease is rare making prospective risk assessment inefficient and expensive, and/or disease has long induction/latent period

true

T/F: Multicenter trials are results from several researchers that are pooled

true

T/F: Outcomes of clinical trials (aka clinical end points) must be measured in a comparable manner in the intervention and control conditions and may include rates of dz, death, or recovery

true

T/F: Placebo / New drug may be added to an existing standard regimen test if the new drug adds to standard therapy in a randomized clinical trial

true

T/F: Relative risk provides a direct measure of association between exposure and outcome.

true

T/F: Intervention studies are used to test efficacy of preventive or therapeutic measures

true (2 types include Randomized clinical trials (RCTs) & Community interventions)

An odds ratio of (0/1/2) implies no association in other words odds of exposure in the cases is the same as the exposure among the controls meaning there is no risk relationship

1

An odds ratio of (0/1/2) suggests cases were twice as likely as controls to be positive for the exposure(s) of interest.

2

Which of the following is a limitation of cohort designs when compared to a RCT? A) Selection bias d/t persons who are positive for exposure not same as unexposed B) Ability to study full spectrum of illness C) Findings more likely to be applicable in real world D) Ability to obtain population-based estimates of exposure effects

A) Selection bias d/t persons who are positive for exposure not same as unexposed (another limitation is the exposures that seem the same but aren't d/t measurement bias or drop-outs/loss to follow-up

Which of the following is NOT a temporal difference in cohort design? A) randomized control trial B) prospective cohort studies C) historical prospective cohort studies D) retrospective cohort studies

A) randomized control trial (a temporal difference is a variation in cohort designs that depend on the timing of data collection)

Which of the following is true of non-inferiority studies? A) Current therapy is effective, but is very costly, lengthy or has major side effects B) Study shows alternate therapies are cheaper, shorter, or safer C) Want to show that the new treatment is not worse. D) Allt he above

D) Allt he above (e.g. comparing a new drug to MTX to prove that this new drug is NOT inferior to MTX)

Which of the following is NOT true of clinical trials? A) Participants in both groups are enrolled, treated, and followed over the same time period. B) Outcomes in treated group are compared with outcomes in an equivalent control group. C) Defined as a planned experiment that assesses the efficacy of a treatment in study subjects. D) Need at least 2 comparative groups E) This is a prospective design

D) Need at least 2 comparative groups (only need 1 comparative group)

Which of the following is NOT true regarding superiority studies? A) Hypothesis is that the new intervention is better. B) New intervention will be adopted if patients' outcomes are better. C) Test new intervention(s) against a known standard or placebo. D) Shows that alternate therapies must be cheaper, shorter, or safer.

D) Shows that alternate therapies must be cheaper, shorter, or safer. (this is true of non-inferiority studies)

Which of the following is not an advantage of case-control studies? A) Can easily accommodate multiple exposure assessments B) Tend to use smaller sample sizes than surveys or prospective studies C) Quick and easy to complete D) Very expensive

D) Very expensive (these are actually very cost effective)

Rank the following study designs in regard to validity from highest to lowest: 1) Retrospective cohort study 2) Experimental study 3) Prospective cohort study A) 1, 2, 3 B) 2, 3, 1 C) 2, 1, 3 C) 1, 3, 2

B) 2, 3, 1

Which of the following is not a characteristic of case-control studies? A) A single point of observation B) Exposure is determined prospectively C) Defined by presence or absence of the outcome in which subjects with the outcome of interest (cases) are selected and a comparable group of subjects without the outcome of interest (controls) are selected and rate of exposure to a specific factor is ascertained in both groups. D) Identifies possible causes of disease by finding out how the two groups differ with respect to exposure to some factor E) Does not directly provide incidence data

B) Exposure is determined prospectively (should be retrospectively)

Which of the following is a strength of clinical trials? A) Artificial setting makes it too control B) Provide the greatest control over the amount of exposure, the timing and frequency of exposure, and the period of observation C) Adherence to protocol is difficult to enforce. D) Ethical dilemmas E) Limited scope of potential impact meaning it may not be realistic for application

B) Provide the greatest control over the amount of exposure, the timing and frequency of exposure, and the period of observation (all others are limitations) (other strength is that the ability to randomize reduces the likelihood that groups will differ significantly)

Which of the following is characterized by determination of exposure levels at baseline (the present), and follow-up for occurrence of disease at some time in the future? A) retrospective cohort studies B) prospective cohort studies C) historical prospective cohort studies

B) prospective cohort studies

Which of the following is a limitation of cohort designs when compared to a RCT? A) Ideal to study natural history, course of disease, prognostic factors B) Conduct etiologic research for exposures that can not be studied experimentally for ethical reasons C) Inability to "blind" the subject or investigator can lead to biased outcome assessment D) Inclusion of "total" population E) Study interventions that are not feasible for randomization such as diagnostic tests

C) Inability to "blind" the subject or investigator can lead to biased outcome assessment

Which of the following is a limitation to cohort studies? A) Permit direct determination of risk. B) Time sequencing of exposure and outcome. C) Take a long time, costly, and subjects are lost to follow-up D) Can study multiple outcomes. E) Can study rare exposures.

C) Take a long time, costly, and subjects are lost to follow-up

Which of the following is not true of crossover designs? A) Defined as any change of treatment for a patient in a clinical trial involving a switch of study treatments. B) In planned crossovers a protocol is developed in advance C) The patient may not serve as his or her own control. D) They're all true

C) The patient may not serve as his or her own control (the pt can serve as his/her own control -- e.g. Person 1: Comparing results in group A and then crosses over to group B and comparing those results)

Which of the following is true of a cohort? A) Cohort group members experience a common exposure associated with a specific setting (e.g., an occupational cohort or a school cohort) B) Cohort group members share a non-specific exposure associated with a general classification (e.g., a birth cohort—being born in the same year or era). C) Defined as a population group, or subset thereof, that is followed over a period of time D) All the above

D) All the above

Which of the following would be a source of a control? A) Patients from the same hospital or clinical population as the cases B) Relatives of cases C) Friends of cases D) All the above

D) All the above (also population-based controls; Goals of control selection include similar to cases as much as possible an representative of population of all controls)

Patient rosters/records, death certificates, Health Surveys, cancer or birth defect registries, incident or prevalent cases are all sources of (cases/controls)

cases (use incident cases when possible; use death certificates when mortality is the outcome being measured)