Biostatistics

Question 1

Selection bias

Answer 1

(recruiting participants)

• Nonrandom assignment of participants in a study group
• MC a sampling bias

Question 2

Selection bias examples (3)

Answer 2

1. Berkson bias: only looking at inpatients
2. Loss to f/u: study of dz w/ early mortality
3. Healthy worker/volunteer bias: study subjects are healthier than gen pop

Question 3

Reducing selection bias (2)

Answer 3

• randomization

- chose appropriate comparison/reference group

Question 4

Performing study bias (4)

Answer 4

Recall
Measurement
Procedure
Observer-expectancy

Question 5

Recall bias and how to reduce it

Answer 5

• 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

Question 6

Measurement bias and how to reduce it (Hawthorne)

Answer 6

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

Question 7

Procedure bias

Answer 7

Subjects in dif groups are not treated the same

Question 8

Observer-expectancy bias

Answer 8

Researcher’s beliefs of tx efficacy changes the outcome (Pygmalion, self-fulfilling prophecy)
- If observer expects a particular outcome, more likely to document it

Question 9

Interpreting results (2)

Answer 9

• Confounding bias

- Lead-time bias

Question 10

Confounding bias and how to fix it

Answer 10

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)

Question 11

Lead-time bias

Answer 11

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)

Question 12

Informed consent involves (4)

Answer 12

Disclosure, understanding, mental capacity and voluntariness

Question 13

Exceptions for informed consent (4)

Answer 13

• 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

Question 14

Core ethical principles (4)

Answer 14

• Respect the patient
• Beneficience
• Nonmaleficence
• Justice

Question 15

Parental consent not needed for

Answer 15

Sex (contraception, STD, preggo)
Drugs (addiction)
Rock’n’Roll (emergency/trauma)

Question 16

Decision making capacity components (6)

Answer 16

• > 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

Question 17

What is an advance directive?

Answer 17

Instructions given by a pt in anticipation of the need for a medical decision (details vary per state law)

Question 18

Oral adv directive

Answer 18

Incapacitate pt’s prior oral statements are used - problems with variance in interpretation

Question 19

Living will

Answer 19

Describes tx a pt wishes to receive or not if they lose decision-making capacity

Question 20

Medical power of attorney

Answer 20

Pt’s agent to make medical decisions. Can be revoked anytime a pt wishes

Question 21

Surrogate-decision maker

Answer 21

If an incompetent pt has not prepared an advance directive, individuals who know the pt well must determine what the pt would have wanted

Question 22

Priority of surrogates

Answer 22

Spouse, adult children, parents, adult siblings, other relatives

Question 23

Confidentiality

Answer 23

Respects a pt privacy and autonomy. May be waived by insurance companies for example

Question 24

Exceptions to confidentiality (4)

Answer 24

• 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

Question 25

Examples of confidentiality exceptions (5)

Answer 25

• 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

Question 26

APGAR score

Answer 26

Assess newborn vital signs following labor via 10-pt scale at 1 and 5 min

Question 27

What does APGAR stand for?

Answer 27

Appearance
Pulse
Grimace
Activity
Respiration

->7 is good
4-6 requires assist and stimulation

Question 28

Low birth weight

Answer 28

Defined as

Question 29

Causes of LBW and complications

Answer 29

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