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Zorluk: ZorMeasures of Association and Impact

A prospective cohort study evaluates the impact of a novel genetic marker on the development of severe coronary artery disease (CAD) over 1010 years. The incidence of CAD is 10%10\% in the exposed group (marker positive) and 2%2\% in the unexposed group (marker negative). The overall incidence of CAD in the entire study population is 3.6%3.6\%. Match each calculated epidemiological value below to its corresponding measure of association or impact.

  • 5.05.0Relative Risk (RR)
  • 8.0%8.0\%Attributable Risk (AR)
  • 80.0%80.0\%Attributable Risk Percent (ARP)
  • 1.6%1.6\%Population Attributable Risk (PAR)
  • 12.512.5Number Needed to Harm (NNH)

Cevap

The correct matches are: 5.0 matches Relative Risk; 8.0% matches Attributable Risk; 80.0% matches Attributable Risk Percent; 1.6% matches Population Attributable Risk; and 12.5 matches Number Needed to Harm.
Each value is mathematically derived from the fundamental incidence rates: Relative Risk is the ratio of exposed to unexposed incidence (5.05.0); Attributable Risk is the absolute difference (8.0%8.0\%); Attributable Risk Percent is the proportion of risk in the exposed due to the exposure (80.0%80.0\%); Population Attributable Risk is the difference between total population risk and unexposed risk (1.6%1.6\%); and Number Needed to Harm is the inverse of the Attributable Risk in decimal form (12.512.5).

Adım Adım Çözüm

1
Extract the relevant incidence rates provided in the study scenario.
Incidence in exposed (IeI_e) = 10%10\%; Incidence in unexposed (IuI_u) = 2%2\%; Total population incidence (ItI_t) = 3.6%3.6\%.
Identifying these baseline parameters is required before applying the formulas for measures of association and impact.
2
Calculate the Relative Risk (RR) and the absolute Attributable Risk (AR).
RR=IeIu=10%2%=5.0RR = \frac{I_e}{I_u} = \frac{10\%}{2\%} = 5.0. AR=Ie−Iu=10%−2%=8.0%AR = I_e - I_u = 10\% - 2\% = 8.0\%.
RR quantifies how many times more likely the outcome is in the exposed, while AR provides the absolute excess risk.
3
Calculate the Attributable Risk Percent (ARP) for the exposed group.
ARP=Ie−IuIe=10%−2%10%=80.0%ARP = \frac{I_e - I_u}{I_e} = \frac{10\% - 2\%}{10\%} = 80.0\%.
ARP determines the fraction of the disease in the exposed group that can be specifically attributed to the genetic marker exposure.
4
Calculate the Population Attributable Risk (PAR).
PAR=It−Iu=3.6%−2.0%=1.6%PAR = I_t - I_u = 3.6\% - 2.0\% = 1.6\%.
PAR evaluates the excess disease incidence in the entire study population that is attributable to the risk factor.
5
Calculate the Number Needed to Harm (NNH).
NNH=1AR=10.08=12.5NNH = \frac{1}{AR} = \frac{1}{0.08} = 12.5.
NNH translates the absolute risk increase into a clinically intuitive metric of how many patients need to be exposed to observe one excess harmful event.

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