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Zorluk: ZorMeasures of Disease Frequency and Association

A state health department is evaluating the public health impact of a carcinogenic chemical used in certain plastic manufacturing processes. A 15-year retrospective cohort study is conducted to assess the association between occupational exposure to this chemical and the development of hepatocellular carcinoma (HCC). The study reveals that the incidence of HCC among workers exposed to the chemical is 200 cases per 100,000 person-years. In contrast, the incidence among workers in the same industry who are not exposed to the chemical is 40 cases per 100,000 person-years. Statewide demographic data indicates that 25% of the total plastic manufacturing workforce is routinely exposed to this chemical. Assuming the association is causal, which of the following best represents the percentage of HCC cases in the total plastic manufacturing workforce that can be attributed to this chemical exposure?

  1. A
    20%
  2. B
    40%
  3. 50%Cevap
  4. D
    62.5%
  5. E
    80%

Cevap

The correct answer is 50%.
The correct answer is 50%. The question asks for the Population Attributable Risk Percent (PARP), which represents the percentage of disease cases in the total population that would be prevented if the exposure were entirely eliminated. It can be calculated using the formula: PARP=It−IuItPARP = \frac{I_t - I_u}{I_t}, where ItI_t is the incidence in the total population and IuI_u is the incidence in the unexposed group. First, calculate ItI_t: (200×0.25)+(40×0.75)=80(200 \times 0.25) + (40 \times 0.75) = 80 cases per 100,000 person-years. Then, calculate PARP: 80−4080=50%\frac{80 - 40}{80} = 50\%. Alternatively, using the Relative Risk (RR=20040=5RR = \frac{200}{40} = 5): PARP=Pe(RR−1)Pe(RR−1)+1=0.25(4)0.25(4)+1=12=50%PARP = \frac{P_e(RR - 1)}{P_e(RR - 1) + 1} = \frac{0.25(4)}{0.25(4) + 1} = \frac{1}{2} = 50\%.

Adım Adım Çözüm

1
Identify the requested epidemiological metric.
The question asks for the percentage of cases in the total workforce attributable to the exposure, which is the Population Attributable Risk Percent (PARP).
Differentiating between Attributable Risk Percent (ARP) for the exposed and PARP for the total population is critical.
2
Extract the given variables from the vignette.
Incidence in exposed (IeI_e) = 200 per 100,000. Incidence in unexposed (IuI_u) = 40 per 100,000. Prevalence of exposure (PeP_e) = 25% or 0.25.
These variables are required to calculate the total population incidence.
3
Calculate the incidence in the total population (ItI_t).
It=(Ie×Pe)+(Iu×(1−Pe))=(200×0.25)+(40×0.75)=50+30=80I_t = (I_e \times P_e) + (I_u \times (1 - P_e)) = (200 \times 0.25) + (40 \times 0.75) = 50 + 30 = 80 cases per 100,000 person-years.
ItI_t serves as the denominator for the PARP calculation.
4
Calculate the Population Attributable Risk Percent (PARP).
PARP=It−IuIt=80−4080=0.50PARP = \frac{I_t - I_u}{I_t} = \frac{80 - 40}{80} = 0.50 or 50%50\%.
This formula isolates the excess risk in the total population and expresses it as a fraction of the total disease burden.

Anahtar Kavram

Population Attributable Risk Percent (PARP)
Tahmini Süre:1m 30s
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Konular

Measures of Disease Frequency and Association

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