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Post by Admin on Jan 24, 2016 23:04:37 GMT
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 prevalence of sickle cell disease in this population?
A. 3/6020
B. 6/100
C. 6/6020
D. 603/6020
E. 606/6100
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Post by Admin on Jan 24, 2016 23:08:46 GMT
What is Prevalence?
Prevalence is the total number of cases in a population divided by the total population at risk of the disease; that is, the proportion of the total population with the disease.
The total number of cases at the beginning of the study can be calculated by multiplying the initial population (?) by the initial prevalence (?), yielding ? cases.
Over the course of the year, there was a net gain of 3 patients with sickle cell disease (6 births and 3 deaths), bringing the new total to ?.
Likewise, the new population at risk is 6020, a net gain of 20 people. Therefore, the current prevalence of sickle cell disease is ?/6020.
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.
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.
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