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#1
08-16-2012
 USMLE Forums Master Steps History: --- Posts: 1,365 Threads: 648 Thanked 584 Times in 354 Posts Reputation: 594
Calculation of Attributable Risk?

In a small observational study, 100 industrial workers are followed for one year to assess for the development of respiratory symptoms (defined as productive cough lasting at least one week). 30 of 60 smokers experience respiratory symptoms over the year versus 10 of 40 non-smokers. What percentage of respiratory disease experienced by all study subjects is attributed to smoking?

A) 75%
B) 50%
C) 25%
0) 20%
E) 10%

#2
08-16-2012
 USMLE Forums Veteran Steps History: Not yet Posts: 218 Threads: 4 Thanked 74 Times in 55 Posts Reputation: 84

draw 2 by 2 table

Dx No Dx
Smok 30 30
Non Smok 10 30

hence 30/40=75%
option Aa
#3
08-16-2012
 USMLE Forums Veteran Steps History: Not yet Posts: 218 Threads: 4 Thanked 74 Times in 55 Posts Reputation: 84

Quote:
 Originally Posted by imgchuchu draw 2 by 2 table Dx No Dx Smok 30 30 Non Smok 10 30 hence 30/40=75% option Aa
oops, distorted table. let me try again

...........................Disease;.........No disease
..........smokers......30;.................30..... ....
..........Non smokers.10;.................30.........
......... Total diseas..40

percentage attributable to smoking 30/40=75%
#4
08-16-2012
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risk of disease in smokers minus the risk of disease in non smoker

30/60 minus 10/40 = 25%
#5
08-16-2012
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C)25%

agree with viral's calculations
#6
08-17-2012
 USMLE Forums Master Steps History: Step 1 Only Posts: 864 Threads: 62 Thanked 370 Times in 224 Posts Reputation: 380

Attributable risk= Incidence of dx - incidence of non dx
So, 30/60 - 10/40 = 1/4= 25%
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#7
08-17-2012
 USMLE Forums Veteran Steps History: Not yet Posts: 218 Threads: 4 Thanked 74 Times in 55 Posts Reputation: 84

wow, hope I don't make this nasty mistake in exam
I was calculating sensitivity instead of AR

 Tags Biostatistics-Epidemiology, Step-1-Questions

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