EBP

Question 1

Differentiate between natural history and clinical course

Answer 1

Natural history: status of the condition without treatment

Clinical course: status of the condition WITH treatment

Question 2

What are the 5 steps in determining prognosis?

Answer 2

1. Ask an answerable question about prognosis
   - P.O.T (population, outcome, time frame)
   - eg. for an obese soccer player with a stress fracture, what is the likelihood of returning to soccer within 3 months
2. Find the evidence
   - prospective/retrospective?
   -
3. Can you believe the study?
4. What is the study of prognosis telling you?
5. Apply the result

Question 3

What are the 3 criteria to believing a study?

Answer 3

1. Representative sample from well defined population?
   - clear inclusion/exlcusion criteria
   - consecutive or ALL pts = representative!
2. Was there an inception cohort?
   - inception cohort = taken at uniform point in the disease
   - survivor cohort = all people with the condition - various stages
3. Complete/near compelete follow up?
   <15% loss (<30% for long term studies)

Question 4

How to calculate odds ratio?

Answer 4

Whatever your prognostic factor is (eg. high and low income) - if you’re looking to see whether low income is a prognostic factor for a certain outcome, put that on TOP

low income: relapsed/non relapsed
high income: relapsed/non relapsed

OR>1 more likely to occur
OR<1 less likely to occur

Question 5

How to calculate CI for prognosis means in CONTINUOUS outcomes?

Answer 5

95% CI = mean +/- 3 * SD/√2N, where N=total number of subjects

Question 6

How to calculate CI for prognosis means in DICHOTOMOUS outcomes?

Answer 6

95% CI = mean +/- 100/√2N, where N=total number of subjects

*use 100 if its written as a percentage (eg. 56%); use 1 if its written as a fraction (eg. 0.56)

REMEMBER TO ACCOUNT FOR DROP OUT WHEN PUTTING IN N!

Question 7

How to calculate risk?

How to calculate CI for risk?

Answer 7

Risk = No. of people with the outcome/total number of people

CI = % risk +/- 100/√2N
- in this case N is the total number of people but only in the group that you were calculating the risk for - NOT the the total number of people in the whole group

Question 8

Prospective vs retrospective

Answer 8

Prospective:
- starts with a group of people and follows them forwards in time; fewer potential sources of bias and confounders; outcome is common

Retrospective:

• looks backwards and examines exposures to suspected risk or protection factors in relation to an outcome that is established at the start of the study
• onfounding and bias are more common