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19 Cards in this Set

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What is a Case Report/Case Series?
Study that tells a "story"
Observational, descriptive
For the purpose of educating others, stimulating further inquiry
What defines a Cross Sectional Study?

Weaknesses?
Subjects sampled at a point in time
Observational but analytic (data!)
Most useful for chronic diseases (HTN, high chol), common diseases (obesity)
Can be used to estimate prevalence of disease process

Commonly done with surveys or questionnaires

Weaknesses:
Not good for rare diseases/exposures
Recall Bias
Sampling bias
What defines a Case Control Study?

Weaknesses?
Persons with condition (cases) are identified, suitable comparison subjects (controls) are identified, and the two groups are compared with respect to prior exposures

Subjects selected based on dz status

Retrospective

Observational, analytic

Good for studying RARE outcomes; efficient in resources and times

Weaknesses:
Selection bias (cases or controls may not be adequately representative)
Recall bias
Difficult to prove cause preceded effect
What defines a cohort study?

Weaknesses?
People without diseases of interest are followed to see if they develop the disease. Disease incidence in persons with a characteristic compared with incidence in persons without the characteristic.

Can be retrospective or prospective

Observational, analytic

Can study multiple diseases

Can estimate incidence based on new cases that develop.

**Better for rare exposures

Weaknesses:
$$$, time consuming if dz is rare or slow to develop
Loss to follow-up (attrition) may lead to selection bias

Relatively statistically inefficient unless dz is common
What groups do prospective/retrospective cohort studies contain?
Prospective cohorts:
Group everyone by EXPOSURE and see if they develop the outcome
(smoking could be an exposure)
What defines a randomized control trial?

Weaknesses?
Experimental
Gold standard for study design

People are randomized into groups

Always prospective

Ideally blinded or double-blinded (study participants and practitioners)

**Most like an experiment, provides STRONGEST evidence for causality in relation to temporality and control

Weaknesses:
Expensive, time consuming, ethically undoable sometimes

May not be able to generalize results (patients tend to be very motivated)
What defines Systematic Reviews and Meta-Analyses?
Conclusion from pooled data from several different studies

Highest statistical power
Cohort Study vs Case-Control Study vs Cross-Sectional Study
Cohort: Exposure-->Outcome

Case-Control: Outcome-->Exposure

Cross-Sectional: Outcome and Exposure measured at same time
What is selection bias?
Bias that occurs when investigators choose which group a study participant is assigned. HAPPENS IN NON-RANDOMIZED STUDIES.
What is recall bias?
The abilituy of one group to recall past inforation is different than the other's

Very prominent in CASE CONTROL STUDIES. People with an illness are more likely to have considered their past behavior than those who are illness free.
What is sampling bias?
happens when chosen study participants are not representative of general population. leads to non-generizable results
What is confounding bias?
When 2 closely related factors obscure real relatinoship between exposure and ouctome--one factor confuses effect of the other (ex: people that have ashtrays in their home are more likely to have heart dz--in actuality, people that smoke; ashtray is a confounding factor)
What is the Pygmalion Effect?
Occurs when a researcher's belief in efficacy of tx changes outcome of tx
What is the Hawthorne Effect?
Occurs when group being studied changes its bhvr owing to knowledge of being studied
What is lead-time bias?
Occurs when earlier detection is confused with increased survival or better outcome (someone gets dx'ed with HTN when 25 and not 45, but would've dev'd heart dz at 55 anyway)
What is length-time bias?
Occurs when disease detected by a screening program is less aggressive than disease detected without screening (breast cancers detected by a screening program may be less aggressive than cancers dx'ed when syx appear)
What is precision?
Consistent reproducibility of a test (reliable); if run a test 100 times, will get same result every time

(want accuracy and precision)
What is accuracy?
Truness of a measurement; validity

(want accuracy and precision)
Describe primary, secondary, and tertiary levels of prevention.

Provide examples of each.
Primary: prevention of dz in entirety, prevention of complications (most cost-effective); ex: IMMUNIZATIONS, FLUORINATED DRINKING WATER, DIET/EXERCISE

Secondary: aimed at early dz detection, and preventing progression of dz. EX: newly diagnosed diabetic: MONITOR BLOOD SUGAR, HgA1C measurement, ROUTINE EYE EXAMS

Tertiary: dz well established, attempting to minimize complications of dz and restore fn. Ex: Patient recently had stroke: SMOKING CESSATION, DAILY ASA, CHOLESTEROL CONTROL, REHAB TO RESTORE FN