Biostatistics Flashcards
Selection bias
(recruiting participants)
- Nonrandom assignment of participants in a study group
- MC a sampling bias
Selection bias examples (3)
- Berkson bias: only looking at inpatients
- Loss to f/u: study of dz w/ early mortality
- Healthy worker/volunteer bias: study subjects are healthier than gen pop
Reducing selection bias (2)
- randomization
- chose appropriate comparison/reference group
Performing study bias (4)
Recall
Measurement
Procedure
Observer-expectancy
Recall bias and how to reduce it
- Awareness of disorder alters recall (common in retrospective, ie: pt with dz recall exposure after learning of similar cases)
- Decrease time from exposure to f/u
Measurement bias and how to reduce it (Hawthorne)
Information is gathered in a way that distorts data
- Hawthorne effect: groups who they know are being studied behave differently than they normally would)
- Use placebo and blinding
Procedure bias
Subjects in dif groups are not treated the same
Observer-expectancy bias
Researcher’s beliefs of tx efficacy changes the outcome (Pygmalion, self-fulfilling prophecy)
- If observer expects a particular outcome, more likely to document it
Interpreting results (2)
- Confounding bias
- Lead-time bias
Confounding bias and how to fix it
3rd factor is related to both exposure and outcome
- Pulm dz more likely in coal miner, however, coal miners are more likely to smoke
- Fix by doing multiple/repeated studies, crossover studies (subjects as their own control), matching (pts with similar characteristics in both tx and control)
Lead-time bias
Early detection is confused with increased survival (seen with improved screening techniques)
Fix: measure back end survival (adjust survival according to severity of disease at time of diagnosis)
Informed consent involves (4)
Disclosure, understanding, mental capacity and voluntariness
Exceptions for informed consent (4)
- Patient lacks decision-making capacity or is legally incompetent
- Emergency
- Therapeutic privilege (witholding info it it would severely harm the apt or undermine decision making)
- Waived
Core ethical principles (4)
- Respect the patient
- Beneficience
- Nonmaleficence
- Justice
Parental consent not needed for
Sex (contraception, STD, preggo)
Drugs (addiction)
Rock’n’Roll (emergency/trauma)
Decision making capacity components (6)
- > 18 or legally emancipated
- Pt makes and communicates choice
- Pt is informed (knows, understands)
- Decision remains stable over time
- Decision is consistent with patient’s values and goals not clouded by a mood disorder
- Decision is not a result of delusions or hallucinations
What is an advance directive?
Instructions given by a pt in anticipation of the need for a medical decision (details vary per state law)
Oral adv directive
Incapacitate pt’s prior oral statements are used - problems with variance in interpretation
Living will
Describes tx a pt wishes to receive or not if they lose decision-making capacity
Medical power of attorney
Pt’s agent to make medical decisions. Can be revoked anytime a pt wishes
Surrogate-decision maker
If an incompetent pt has not prepared an advance directive, individuals who know the pt well must determine what the pt would have wanted
Priority of surrogates
Spouse, adult children, parents, adult siblings, other relatives
Confidentiality
Respects a pt privacy and autonomy. May be waived by insurance companies for example
Exceptions to confidentiality (4)
- Potential physical harm to others is serious or imminent
- Likelihood to harm self is great
- No alternative means exists to warn or protect those at risk
- Physicians can take steps to prevent harm
Examples of confidentiality exceptions (5)
- Reportable diseases (STD, TB, hep, food poisoning)
- Tarasoff (required physicians to warn and protect potential victims of harm)
- Child and elder abuse
- Impaired automonile drivers (epileptics too)
- Suicidal and homicidal patients
APGAR score
Assess newborn vital signs following labor via 10-pt scale at 1 and 5 min
What does APGAR stand for?
Appearance Pulse Grimace Activity Respiration
->7 is good
4-6 requires assist and stimulation
Low birth weight
Defined as
Causes of LBW and complications
Prematurity or IUGR
- Associated with increased risk of SIDS and overall mortality
- Impaired thermoreg and immunity, hypoglycemia, polycythemia, impaired neurocog/emotional development
- Complications: infections, resp distress, necrotizing enterocolitis, intraventricular hemorr, persistent fetal circulation
