Epidemiology problem: School-based sealant programs are recommended by the CDC a
ID: 3203800 • Letter: E
Question
Epidemiology problem:
School-based sealant programs are recommended by the CDC and target populations that may be at greater risk for developing decay and less likely to receive preventive care. A school-based sealant program was implemented in East Palo Alto in an effort to reduce the number of new dental caries (cavities) among children without any dental care. In September 2014, 750 children were enrolled in this program. All of these children were screened for dental caries at the beginning of the school year when they were enrolled, and 125 were found to have dental caries. Sealants were provided to all 750 children though current cavities were not filled. When the same 750 children are screened again in September 2016, 140 are found to have dental caries.
a. What was the prevalence of dental caries in this population in September 2014?
b. What was the prevalence of dental caries in this population in September 2016?
c. Program evaluators want to know the risk of moving from the category of having no dental caries to having at least one over the period of time between the September 2014 and September 2016 in this group of children? What type of measure of disease occurrence measures risk?
Explanation / Answer
Answer)
a) The prevalene of dental caries in the population in September 2014 is calculated as:
Prevalence = Number of Cases / Population Size
Prevalence2014 = 125 / 750 = 0.1667
Therefore, prevalence for 750 people is 0.1667*750 = 125.025
Approximately equal to 125 persons
b) The prevalence of dental caries in the population in September 2016 is calculated as:
Prevalence2016 = 140 / 750 = 0.1867
Therefore, Prevalence for 750 persons is 0.1867*750 = 140.025
Approximately equal to 140 persons
c) Incidence Rate is very helpful to measure the occurence of risk.
The risk of moving from the category of having no dental caries to having atleast one over period of time between the September 2014 and September 2016 in the group of children is measured using Incidence Rate.
Incidence Rate is a measure of frequency with which a disease occurs in a population over a period of time.
Incidence Rate is calculated as below:
Incidence Rate/Incidence Density = (New cases occuring during a time of period) divided by
(Population at risk during the same time period)
Among the total population of 750, 125 were found to have dental caries. Therefore, healthy population = 625
In the next two years,among 750 people 140 were found to have the disease. Therefore, 15 people developed the disease.(140-125)
Therefore, New Cases occurring during a time of period 2 is 15.
Population at risk in the same time period = 625
Incidence Rate = 15 / (625*2 years) = 0.012/year.
equivalently, 1 person among every 100 persons
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