PHC 6001 Chapter 2 (Exam)

differences between prevalence and incidence

*incidence rate* is a true rate that directly integrates person time of observation into the denominator; *cumulative incidence* is a proportion whose denominator is the population at risk at the start of the observation period, where time is expressed only by words that go along with the proportion.

810 person years

A population of 100 healthy men was followed for the development of prostate cancer. After being followed for 5 years, 20 men developed prostate cancer. Another 10 men were followed for 1 year and then were lost. The remaining men who never developed the disease were followed for 10 years. Calculate the number of person-years of observation accrued by this population.

d

A study of 100 durg users who tested - HIV injection at enrollment and 3 month intervals during 2 year period; the injection drug users were followed for the entire 2 year period, none died and none were lost to follow up. Which frequency measure of HIV infection can be calculated at the end of this study? a. prevalence b. cumulative incidence c. incidence rate d. all of the above

incidence rate =

A total of 60 cases of myocardial infarction were reported over a period of 2 years in a city with a population of 100,000 person - years. Using these data, estimae the incidence rate of myocardial infarction per 100,000 person - years. State any assumptoions that are needed.

.05 or 5%

Consider a class with 100 enrolled students. None of the students were ill at the beginning of the school year. On Sept. 30, a total of 5 students reported having gastroenteritis. All 5 continued to be ill on Oct. 1, but all 5 recovered within 3 days. On Oct. 14, another 3 students developed gastroenteritis. In this example assume that a person cannot get gastroenteritis more than once. a. calculate the prevalence of gastroenteritis in the class on oct 1.

0/100

Consider a class with 100 enrolled students. None of the students were ill at the beginning of the school year. On Sept. 30, a total of 5 students reported having gastroenteritis. All 5 continued to be ill on Oct. 1, but all 5 recovered within 3 days. On Oct. 14, another 3 students developed gastroenteritis. In this example assume that a person cannot get gastroenteritis more than once. b. calculate the prevalence of gastroenteritis in the class on oct 30

3/95

Consider a class with 100 enrolled students. None of the students were ill at the beginning of the school year. On Sept. 30, a total of 5 students reported having gastroenteritis. All 5 continued to be ill on Oct. 1, but all 5 recovered within 3 days. On Oct. 14, another 3 students developed gastroenteritis. In this example assume that a person cannot get gastroenteritis more than once. c. Calculate the cumulative incidence of gastroenteritis in the class during the month of october.

A: 25/25000 B: 30/50000

Consider the data for occurrence of hepatitis in two cities: A = 25 new cases from Jan-Dec 2017; starting pop at risk 25000 B = 30 new cases from Jan-Dec 2017; " " 50,000 a. Calculate the cumulative incidence of hepatitis in each city.

A

Consider the data for occurrence of hepatitis in two cities: A = 25 new cases from Jan-Dec 2017; starting pop at risk 25000 B = 30 new cases from Jan-Dec 2017; " " 50,000 b. Which city has the higher cumulative incidence?

incidence rate

Name the disease frequency: The number of live born babies who die of sudden infant death syndrome during the first year of life per 100000 baby years of follow up

cumulative incidence

Name the disease frequency: The percentage of infants weighing less than 2500 grams at birth

cumulative incidence

Name the disease frequency: The percentage of of freshman girls who become pregnant over the course of their high school years.

prevalence

Name the disease frequency: The percentage of senior boys who are fathers at the time of graduation

P=IRxD or 1500/100,000

The incidence rate of a nonfatal disease is 500/100,000 person years. People usually have the disease for an average of 3 years, at which time the disease resolves spontaneously. Estimate the prevalence of this disease using this information. Assume the population is in steady state.

a. prevalence b. incidence

_____a_______ : quantifies existing cases ______b_______ : quantifies new cases

similarities of prevalence and incidence

both quantify the number of new cases of disease that develop in a population at risk during a specific period of time

dynamic population

defined by a changeable state or condition, and therefore its embership is transitory

fixed population

defined by a life event and therefore its membership is permanent

cannot

incidence rate must have both a numerator and a denominator to calculate; therefore when the number of diseased is the only value you can/not calculate the incidence of a disease.

0-1 or 0-100%

range for cumulative incidence

0-infinity

range for incidence rate

0-1 or 0-100%

range for prevalence