Biostats Flashcards
Post test probability
Pre test prob is 10%
liklihood ratio is 16
Post test probability
10% pre test porbablity = 1:9 odds
16 is lilihood ratio
16+9=25
16/25= post test proabiliy
Minors <18 yrs old excpetions to needing parental consent
- married
- preggo
- finacially indpendent
- riaisng kid
- living by theirself
- in the army
- OCPs or Pregnancy Tx
- STD
- Psych illness
*need parental consent for abortions
difference in comeptency vs capaacity
Competent= legal by court
-permanent is dementia and someone appointed b court ot make decisions, dleirum is temporary
capacity = medical by me
break of confidentiality (2)
- hurt themselves or others
2. Abuse
termnally ill patients make sure you prescribe
LOTS of opiods
Make sure to rpeort HIV aids, syph, measles all the good stuff
withdrawal of care anf amily disagrees with patient?
seek out ethics comittee
High sensitivity but low spec= False ____
High spec but low sens= False____
Positive
Negative
95% sens 95% spec Low prevalence of disease 1% 10% 50% 90%
1- not helpful
2- Kinda helpful, negative result reduces lieklihood and positve test says it needs more tests
3- Very helpful
4- not helpful- positive adds ntohign and negative is a false negative
Disease present Disease absent
+/exposure A B
-/no exp C D
Know it
Specificity Equation
D/ D+B
PPV equation
A/ A+B - liklihoood a positive result is positive
High prevelance== higher PPV\
Need cohort study not case control- incidence needs to reflect he population
NPV equation
D/ C+D - liekly hoood the negaitve result is disease free
Lower pevelance = higher NPV
Need cohort study not case control- incidence needs to reflect he population
Incidence define
new cases per year
prevalence define
total number of existing cases in a population at certin snap shot of time
Absolute risk define
PROBABILTY of n event occuring over a time frame
1% chnce of getting Disease X in 5 years
Relative risk define
COHORT porspective studies comapring groups exposed to a risk factor or not
RR<1 in event less liekly in exposed group
RR>1 exposed group more likely to have event
Odds ratio defined
CASE CONTROL studies, RETROSPECTIVE studies.
it compares rate of epxosure to those with and without disease. Less accruate than OR
Relative rate equation
a/a+b /// c/c+d
Odds ratio equation
AD/BC
Absolute risk reduction define and equation
Risk from exposure to something + Background of disease.
RANDOMIZED CONTROL TRIALS. BEST EQUATION AND WAY BETTER THAN RRR
Absolute risk (adverse events) in placebo group - absolute risk in treated patients
Absolute risk reduction define and equation
Risk from exposure to something + Background of disease.
RANDOMIZED CONTROL TRIALS. BEST EQUATION for benefit AND WAY BETTER THAN RRR
Absolute risk (adverse events) in placebo group - absolute risk in treated patients
RRR
RADNOMIZED CONTORL TRIALS
ratio between 2 risks
Ratio and can look deceptively large
event rate in control - event rate in experimental patients /// event rate in control
Or Unexposed-exposed///unexposed
Example of ARR AND RRR
reduction of adverse event is 0.01% to 0.004%
ARR 0.01-0.004 = 0.006%
RRR 0.01-0.004///0.01= 0.6 or 60%!!!
NNT define and equation
number of patients ot be treated to prevent 1 adverse event
1/ARR