Examkin

Soru

Zorluk: OrtaMeasures of Disease Frequency

A public health research team conducts a 22-year prospective cohort study to evaluate the incidence of newly diagnosed hypertension in a specific community. The study enrolls 1,0001,000 healthy volunteers, all of whom are screened and confirmed to be free of hypertension at baseline.

During the first year, 5050 patients are diagnosed with hypertension, and 100100 patients move away and are lost to follow-up.
During the second year, an additional 7070 patients are diagnosed with hypertension. There are no further losses to follow-up in the second year.

Assume that all new diagnoses of hypertension and all losses to follow-up occur uniformly throughout the year (i.e., individuals contribute an average of 0.50.5 person-years during the year their event or drop-out occurs).

Based on these data, which of the following is the correct incidence rate of hypertension in this study?

  1. A
    60.060.0 per 1,0001,000 person-years
  2. B
    63.563.5 per 1,0001,000 person-years
  3. 69.069.0 per 1,0001,000 person-yearsCevap
  4. D
    120.0120.0 per 1,0001,000 person-years
  5. E
    153.8153.8 per 1,0001,000 person-years

Cevap

The correct incidence rate is 69.069.0 per 1,0001,000 person-years.
The incidence rate (incidence density) is calculated by dividing the number of incident cases by the total person-time at risk. By correctly accounting for the midpoint assumption, Year 1 yields 925925 person-years (850850 complete + 50×0.550 \times 0.5 cases + 100×0.5100 \times 0.5 dropouts) and Year 2 yields 815815 person-years (780780 complete + 70×0.570 \times 0.5 cases). The total person-time is 1,7401,740 person-years. Dividing the 120120 total cases by 1,7401,740 person-years results in a rate of 69.069.0 per 1,0001,000 person-years.

Adım Adım Çözüm

1
Calculate the person-years (PY) contributed during Year 1.
Year 1 PY = 925925.
The study starts with 1,0001,000 people. 5050 get the disease (contributing 0.50.5 years each = 2525 PY). 100100 are lost to follow-up (contributing 0.50.5 years each = 5050 PY). The remaining 850850 complete the year disease-free (850×1=850850 \times 1 = 850 PY). Total = 25+50+850=92525 + 50 + 850 = 925 person-years.
2
Calculate the person-years (PY) contributed during Year 2.
Year 2 PY = 815815.
Year 2 starts with 850850 people. 7070 get the disease (contributing 0.50.5 years each = 3535 PY). The remaining 780780 complete the year (780×1=780780 \times 1 = 780 PY). Total = 35+780=81535 + 780 = 815 person-years.
3
Calculate the total incident cases and total person-years for the entire study.
Total cases = 120120. Total PY = 1,7401,740.
Total cases = 5050 (Year 1) + 7070 (Year 2). Total PY = 925925 (Year 1) + 815815 (Year 2).
4
Calculate the incidence rate (incidence density).
120/1,740=0.06896120 / 1,740 = 0.06896 cases per person-year, or approximately 69.069.0 per 1,0001,000 person-years.
Incidence rate is defined as the number of new cases divided by the total person-time at risk during the observation period.

Anahtar Kavram

Incidence rate (incidence density) measures the frequency with which a new disease occurs within a population over a specific period of time, utilizing person-time at risk as the denominator to account for dynamic populations and losses to follow-up.
Tahmini Süre:2m 0s
Bu soruyu puanla

Konular

Measures of Disease Frequency

Bu konudan daha fazla soru