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#1
10-08-2012
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 307 Threads: 36 Thanked 127 Times in 61 Posts Reputation: 137
ARR vs. RRR?

Is Relative Risk Reduction (RRR) the same as Absolute Risk reduction (ARR)? I wasn't aware of RRR till I just saw a UW question.
The formula is: RRR= [Absolute risk(control)-Absolute risk(treatment)] / Absolute risk(control)

Can someone explain if they understand how is it different from Absolute Risk Reduction (ARR)?

#2
10-08-2012
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 307 Threads: 36 Thanked 127 Times in 61 Posts Reputation: 137

Anyone!
#3
10-08-2012
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 394 Threads: 40 Thanked 218 Times in 99 Posts Reputation: 228

This concept really confuses me.. I ll try to explain..

ARR= (event rate in control group)-(event rate in Study group)
but it sound same as Absolute risk

Number need to treat= 1/ARR which gives the Number of pt to be treated to reduce occurrence of One case

====================================

RRR is % by which the drug reduces incidence in those on treatment compared to control group:
i.e,

RRR= (risk in control -risk in treatment)/(risk in control)
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 The above post was thanked by: adeelsaleemi (10-09-2012), dockhi (10-09-2012)
#4
10-09-2012
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 307 Threads: 36 Thanked 127 Times in 61 Posts Reputation: 137

Wow, thanks!
Also, (just to get a better concept, pardon my stupidity), when we say 'treatment group and 'control group'. Is it the same as saying 'exposed' and 'non-exposed' respectively?
#5
10-09-2012
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 394 Threads: 40 Thanked 218 Times in 99 Posts Reputation: 228
I

They are different ...

Treatment grp and control group .. Both groups are similar in terms of having certain disease and one group recieves an intervention like medication or life style modification while other doesn't ...eg, two groups of Obese subjects: one group given sinistermine while placebo to other.. Used usually in clinical trials where the Intervention is tested for its efficacy

While

Exposed and non-exposed groups ... both groups are comparable but one has certain kind of exopsure eg, group smoker with another group of non-smokers but are comparable in terms of age, sex, race etc... more so in observational study like Cohort study where the Risk of developing a disease wrt certain exposure is studied.
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 Tags Biostatistics-Epidemiology

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