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#1
12-01-2011
 USMLE Forums Addict Steps History: Not yet Posts: 101 Threads: 21 Thanked 11 Times in 10 Posts Reputation: 21
Incidence and prevalence Question

1000 patients are enrolled from a community with recurrent HSV infections and are randomized: 500 recieve the new drug and 55 recieve the placebo. The results are that the average duration of recurrent HSV outbreaks in the new drug group is 1 week, compared with 2 weeks in the placebo group. Which of the following outcomes regarding symptomatic HSV infections is most likely in the greater population if all affected patients in the community are treated with the new drug?
a) incidence will decrease by half
b) incidence will double
c) prevalence will decrease
d) prevalence will double

At first i thought it was b because each week the patients are getting reinfected again but then i thought since they were getting reinfected it means they are not new cases? or are they? so that cancels out incidence (answer b) so does this mean it's prevalence which is answer d?

thanks so much

#2
12-01-2011
 USMLE Forums Veteran Steps History: Step 1 Only Posts: 277 Threads: 36 Thanked 159 Times in 95 Posts Reputation: 169

1000 patients are enrolled from a community with recurrent HSV infections and are randomized: 500 recieve the new drug and 55 recieve the placebo. The results are that the average duration of recurrent HSV outbreaks in the new drug group is 1 week, compared with 2 weeks in the placebo group. Which of the following outcomes regarding symptomatic HSV infections is most likely in the greater population if all affected patients in the community are treated with the new drug?
a) incidence will decrease by half
b) incidence will double
c) prevalence will decrease
d) prevalence will double

incidence are NEW cases for a given time.
Prevalance on the other hand is cases already present.

if I were treating all affected with the new drug - those are the prevelant population- so if I try to prevent new outbreaks ( that is symptomatic ) I would be decreaseing the incidence.

Am I correct?
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#3
12-01-2011
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The answer is not a as I originally put A but it was marked wrong

#4
12-01-2011
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I cry the Answer is C
#5
12-01-2011
 USMLE Forums Scout Steps History: 1 + CS Posts: 99 Threads: 27 Thanked 72 Times in 31 Posts Reputation: 82

Average duration is decreased from 2 week to 1 week ..it means that prevalence is decreased..
#6
12-01-2011
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C . .. . ......
#7
12-01-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 342 Threads: 50 Thanked 197 Times in 103 Posts Reputation: 207

source of question?
#8
12-02-2011
 USMLE Forums Addict Steps History: Not yet Posts: 101 Threads: 21 Thanked 11 Times in 10 Posts Reputation: 21

Is it prevalence because the patients are getting reinfected? So then the reinfected doesn't count for the the new cases

 Tags Biostatistics-Epidemiology, Step-1-Questions

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