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  #1  
Old 09-23-2014
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Default Biostat question for the day

A research group is studying sickle cell disease in a geographically isolated community of 6000 people. A genetic analysis is performed on every community member. At the beginning of the year, it is determined that 10% are homozygous for hemoglobin S and therefore have sickle cell disease, and 30% of the community is heterozygous for the mutant allele. Over the course of the year, 100 infants are born, six of whom are diagnosed with sickle cell disease. Of the 80 people who die during the year, three had sickle cell disease.
Which of the following is the current incidence rate of sickle cell disease in this population?



A. 6/3600
B. 6/100
C. 6/5400
D. 603/6020
E. 6/3620
F. 6/5420
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shudnt it b 6/6020..?

though of course der s no such option there..!

6 new cases andtotal population 6000+(100-80)
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Obviously ones its not there, u got to take another answer!
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  #4  
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D. 603/6020
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My answer is EE

Thanks for the question
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It's tricky guys. More answers! You are all doing very well.
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Quote:
Originally Posted by nsesereso View Post
A research group is studying sickle cell disease in a geographically isolated community of 6000 people. A genetic analysis is performed on every community member. At the beginning of the year, it is determined that 10% are homozygous for hemoglobin S and therefore have sickle cell disease, and 30% of the community is heterozygous for the mutant allele. Over the course of the year, 100 infants are born, six of whom are diagnosed with sickle cell disease. Of the 80 people who die during the year, three had sickle cell disease.
Which of the following is the current incidence rate of sickle cell disease in this population?



A. 6/3600
B. 6/100
C. 6/5400
D. 603/6020
E. 6/3620
F. 6/5420
10% are homozygous and 30% are heterozygous mutants. So 600 + 1800 = 2400 cannot be at risk of having the disease. (we subtract it from denominator).
Now, 100 are born but 6 had SCD. so we add 94 to the denominator.
80 died but 3 had SCD. So we substract 77 from denominator
So my denominator is 6000 - 2400 +94 -77 = 3617
Numerator is 6

I donno what am I missing here
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Quote:
Originally Posted by DrNewB View Post
10% are homozygous and 30% are heterozygous mutants. So 600 + 1800 = 2400 cannot be at risk of having the disease. (we subtract it from denominator).
Now, 100 are born but 6 had SCD. so we add 94 to the denominator.
80 died but 3 had SCD. So we substract 77 from denominator
So my denominator is 6000 - 2400 +94 -77 = 3617
Numerator is 6

I donno what am I missing here
Nooooooooooooo all this is wronggg. How can someone who dont have the disease become at risk. This is not an acquired disease.
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My answer is AA
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Quote:
Originally Posted by DrNewB View Post
My answer is AA
Your reasoning pattern is excellent!
U got the concepts right. But u are just a little bit from the answer?
Am impressed. U know its not acquired but u picked wrong answer!
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Quote:
Originally Posted by nsesereso View Post
A research group is studying sickle cell disease in a geographically isolated community of 6000 people. A genetic analysis is performed on every community member. At the beginning of the year, it is determined that 10% are homozygous for hemoglobin S and therefore have sickle cell disease, and 30% of the community is heterozygous for the mutant allele. Over the course of the year, 100 infants are born, six of whom are diagnosed with sickle cell disease. Of the 80 people who die during the year, three had sickle cell disease.
Which of the following is the current incidence rate of sickle cell disease in this population?



A. 6/3600
B. 6/100
C. 6/5400
D. 603/6020
E. 6/3620
F. 6/5420
I think that the answer is "F".

Incidence rate = No. of new cases in a year/ population at risk in that year

No. of new cases = 6 (Because 6 infants with sickle cell disease is born)

To calculate population at risk ...
Firstly, Total population - People with sickle cell disease = 6000 - 600 = 5400
Secondly, 540 + No. of newly born infants in that year = 5400 + 100 = 5500
Then, 640- No. of total death in the year = 5500 - 100 = 5420

Therefore, total population at risk = 5420

Lastly,

Incidence rate = 6/5420
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Oops... I think that I have got wrong in my previous answer.

The correct answer should be "B".

Because only the newborn infants are at risk.
Is it true?
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It's urx question which I modified a little bit.

Yea answer is B.


Prevalence is commonly confused with incidence, which is the number of new cases in a unit of time divided by the number of susceptible people. Choice B represents the incidence of sickle cell disease during the year, Because the genotype of all community members is already known, only newborn infants are truly at risk for the disease. Therefore, of the 100 people at risk for sickle cell disease, 6 were diagnosed, yielding an incidence of 6/100.
The prevalence is 603/6020
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Lessons learned - Don't over-think and don't get distracted by excess information.
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Oh no i m late just seen the question but i would choose B too
Cuz 100 are at risk this year 6 are the new cases. In the last two lines the clearly mentioned this year so it means they are talking about the current incidence means this year incidence cuz rest will be prevelance. I tackle this type of question before not the same but kind is same. They confuse us with alot of numbers distractors.
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  #16  
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Quote:
Originally Posted by Dr.ann View Post
Oh no i m late just seen the question but i would choose B too
Cuz 100 are at risk this year 6 are the new cases. In the last two lines the clearly mentioned this year so it means they are talking about the current incidence means this year incidence cuz rest will be prevelance. I tackle this type of question before not the same but kind is same. They confuse us with alot of numbers distractors.
Sorry my friend! I think next time I should wait for minimum of 24hrs before giving answers!
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