¶ … Population of the City of Atlantis on March 30, 2003 = 183,000 of new active cases of TB occurring between January 1 and June 30, 2003 = 52

of active TB cases according to the city register on June 30, 2003 = 238

The incidence rate of active cases of TB for the 6-month period was: [ONE POINT]

per 100,000 population per 100,000 population per 100,000 population per 100,000 population

130 per 100,000 population

183,000 is 183% of 100,000, so the rate per 100,000 would be 52 divided by 1.84...or 28.

The prevalence of active TB as of June 30, 2003, was: [ONE POINT]

14 per 100,000 population

130 per 100,000 population

144 per 100,000 population

264 per 100,000 population

e. none of the above

B -- using the same math as above...except it's 238 / 1.84 -- 129.3

3. Which of the following is an advantage of active surveillance? [ONE POINT]

a. requires less project staff

b. is relatively inexpensive to employ

c. more accurate due to reduced reporting burden for health care providers

d. relies on different disease definitions to account for all cases

e. reporting systems can be developed quickly

C -- page 38 in the source material...chapter 3.

Question 4 is based on the information given below:

In an Asian country with a population of 10 million people, 80,000 deaths occurred during the year ending December 31, 2005. These deaths included 50,000 deaths from cholera in 90,000 people who were sick with cholera.

4. What was the case-fatality rate from cholera in 2005? [ONE POINT]

It would be 55%. There were 50,000 deaths from cholera and that was from a wider pool of 90,000. 50,000 is 55% of 90,000.

5. What would be the effect on age-specific incidence rates if women with hysterectomies were included in the denominator of calculations, assuming that there are some women in each age group who have had hysterectomies? [ONE POINT]

a. the rates would remain the same

b. the rates would tend to decrease

c. the rates would tend to increase

d. the rates would increase in older groups and decrease in younger groups

e. it cannot be determined whether the rates would increase or decrease

E -- need more data. If it is accepted that there are people in each group, the rate variation would vary based on the number of applicable women in each group. To know the rates, the numerator AND the denominator would need to be known for each group that is under review.

Question 6 is based on the following information:

A colon cancer screening study is being conducted in Nottingham, England. Individuals 50 to 75 years old will be screened with the Hemoccult test. In this test, a stool sample is tested for the presence of blood.

6. If the Hemoccult test result is negative, no further testing is done. If the Hemoccult test result is positive, the individual will have a second stool sample tested with the Hemoccult II test. If this second sample also tests positive for blood, the individual will be referred for more extensive evaluation. What is the effect on net sensitivity and net specificity of this method of screening? [ONE POINT]

a. Net sensitivity and net specificity are both increased

b. Net sensitivity is decreased and net specificity is increased

c. Net sensitivity remains the same and net specificity is increased

d. Net sensitivity is increased and net specificity is decreased

e. The effect on net sensitivity and net specificity cannot be determined from the data

B - https://prezi.com/v4hgmes6tnly/use-of-multiple-tests-two-stage-testing-simultaneous-testing-net-sensitivity-net-specificity/

7. At an initial examination in Oxford, Mass., migraine headache was found in 5 of 1,000 men aged 30 to 35 years and in 10 of 1,000 women aged 30 to 35 years. The inference that women have a two times greater risk of developing migraine headache than do men in this age group is: [ONE POINT]

a. correct

b. incorrect, because a ratio has been used to compare male and female rates

c. incorrect, because of failure to recognize the effect of age in the two groups

d. incorrect, because no data for a comparison or control group are given

e. incorrect, because of failure to distinguish between incidence and prevalence

A -- The sample is the same size and the age group is the same size...it is only the incidence rate that is different. As such, it is indicated that the rate is doubled.

8. Age-adjusted death rates are used to: [ONE POINT]

a. Correct death rates for errors...

Determine the actual number of deaths that occurred in specific age groups in a population
c. Correct death rates for missing age information

d. Compare deaths in persons of the same age group

e. Eliminate the effects of differences in the age distributions of populations in comparing death rates

E - http://health.mo.gov/data/mica/CDP_MICA/AARate.html - People that are older, by definition, are going to die more often by virtue of their age. As such, the rates for each age group have to be adjusted to reflect the death rates since they will ALWAYS be higher for older people. It allows for comparisons between populations that have younger populations and older populations.

9. The mortality rate from disease X in city A is 75/100,000 in persons 65 to 69 years old. The mortality rate from the same disease in city B. is 150/100,000 in persons 65 to 69 years old. The inference that disease X is two times more prevalent in persons 65 to 69 years old in city B. than it is in persons 65 to 69 years old in city A is: [ONE POINT]

a. Correct

b. Incorrect, because of failure to distinguish between prevalence and mortality

c. Incorrect, because of failure to adjust for differences in age distributions

d. Incorrect, because of failure to distinguish between period and point prevalence

e. Incorrect, because a proportion is used when a rate is required to support the inference

B -- the two rates are about mortality (death) while the stated inference is about PREVALENCE. Getting the disease and dying from it are NOT the same thing and thus the inference is invalid. It WOULD be correct, however, to say that the MORTALITY rate was twice as much.

10. For a disease such as pancreatic cancer, which is highly fatal and of short duration: [ONE POINT]

a. Incidence rates and mortality rates will be similar

b. Mortality rates will be much higher than incidence rates

c. Incidence rates will be much higher than mortality rates

d. Incidence rates will be unrelated to mortality rates

e. None of the above

A -- if the disease is quick to kill and that is usually what happens, the rates will be very close. For example, of 100 people get pancreatic cancer and 95 die, that is a mortality rate of 95% and the numerator and denominator are quite close together. However, what would NOT be seen is those two parts of the fraction being disparate. Further, mortality rates can never be higher than incident rates (B), C cannot be true for the reasons already explained and they are absolutely related. A is clearly the correct answer.

11. In 1990, there were 5,000 deaths due to lung diseases in miners aged 20 to 64 years. The expected number of deaths in this occupational group, based on age-specific death rates from lung diseases in all males aged 20 to 64 years, was 2,500 during 1990.

a. What was the standardized mortality ratio (SMR) for lung diseases in miners? [ONE POINT]

SMR is observed deaths over expected...or 2 in this case (5000 / 2500)

https://ibis.health.state.nm.us/resource/SMR_ISR.html

b. Interpret the value of the SMR: [ONE POINT]

Excess deaths as the value is greater than one.

https://ibis.health.state.nm.us/resource/SMR_ISR.html

Questions 12-15 are based on the information given below:

A physical examination was used to screen for breast cancer in 2,700 women with biopsy-proven adenocarcinoma of the breast and in 5,200 age- and race-matched control women. The results of the physical examination were positive (i.e., a mass was palpated) in 2,000 cases and in 500 control women, all of whom showed no evidence of cancer at biopsy.

12. The sensitivity of the physical examination was: [ONE POINT]

The Bayesian square that should be used in this instance is as follows

2000 -- True Positive

500 -- False Positive

2500 -- Test Positive

700 -- False Negative

4700 -- True Negative

5400 -- Test Negative

34% - T Disease (2700/7900)

66% - T Non-Disease (5200/7900)

100% (7900/7900)

Sensitivity would be 2000 / (2000 + 700) * 100 = 2000 / 2700 * 100 = 74.07%

13. The specificity of the physical examination was: [ONE POINT]

Specificity would be 4700 / (4700 + 500) * 100 = 90.38%

14. The positive predictive value of the physical examination was: [ONE POINT]

PPV would be 2000 / (2000 + 500) * 100 = 2000 / 2500 * 100 = 80%

15. The negative predictive value of the physical examination was: [ONE POINT]

Would be 4700/(4700 + 700) * 100 = 4700 / 5400 * 100 = 87.04%

https://onlinecourses.science.psu.edu/stat507/node/71

Question 16 is based on the following information:

A physical examination and an audiometric test were given to 500 persons with suspected hearing problems, of whom 300 were actually found to have them. The results of the examinations were as follows:

PHYSICAL EXAMINATION

HEARING PROBLEMS

Result Present Absent

Positive 270 40

Negative 30 160

AUDIOMETRIC TEST

HEARING PROBLEMS

Result Present Absent

Positive 280 20

Negative 20 180

16. Compared with the physical examination, the audiometric test is: [ONE POINT]

a. Equally sensitive and specific

b. Less sensitive and less specific

c. Less sensitive and…