100 people with hypertension are followed up for 5 years to observe for development of myocardial infarction. At the end of second year 5 people develop myocardial infarction, at the end of third year another 2 people develop myocardial infarction and at the end of five years 3 people develop myocardial infarction. Calculate the incidence rate of myocardial infarction.
a) 10 cases per five person-years
b) 10 percentage
c) 10/481 cases per person-year
d) 10/500 cases per person-year
Answers
Answer:
Explanation:
100 people with hypertension are followed up for 5 years to observe for development of myocardial infarction
The correct answer for incidence rate of myocardial infarction is 10/500 cases per person-year (option d).
Given:
Number of people who are at risk of Myocardial Infarction under study= 100
Time-frame of study= 5 years
Cases in subsequent years= 5 cases (at end of 2nd year)
=2 cases (at end of 3rd year)
= 3 cases (at end of 5th year)
To Find:
Incidence rate of myocardial infarction= ?
Step-wise solution:
The number of new cases that occurred within a certain time period divided by the total number of people at risk of contracting a disease is referred to as the incidence rate.
Incidence rate can be calculated from the following formula:
Incidence rate= (New Cases) / (Population x Timeframe)
Now to find incidence rate steps are as follows:
The follow-up period= 5 years
The total number of new cases reported in 5 years= 5 + 2 + 3 cases (given)
= 10 cases
Incidence rate= 10 cases / (100 people × 5 years)
= 10 cases / 500 person year (or)
= 10/500 cases per person-year
The incidence rate is usually calculated as cases per person-year because it takes into account total study population as well as time frame of study.
Hence, 10/500 cases per person-year is the incidence rate of Myocardial Infarction.