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Zorluk: OrtaMeasures of Association and Impact

Researchers at a multi-institutional nephrology consortium are evaluating the efficacy of a novel nonsteroidal mineralocorticoid receptor antagonist in preventing renal failure progression. They enroll a cohort of individuals with type 2 diabetes and advanced chronic kidney disease. The participants are divided equally into an intervention arm and a standard-of-care control arm, with 1,2001,200 subjects in each cohort. Over a 55-year longitudinal observation period, the primary outcome of progression to hemodialysis dependence occurs in 180180 patients receiving the intervention and 240240 patients receiving standard care alone. Based on this data, which of the following represents the relative risk reduction (RRR) and the number needed to treat (NNT) to prevent one case of hemodialysis dependence?

  1. Relative risk reduction: 25%25\%; Number needed to treat: 2020Cevap
  2. B
    Relative risk reduction: 75%75\%; Number needed to treat: 2020
  3. C
    Relative risk reduction: 5%5\%; Number needed to treat: 2020
  4. D
    Relative risk reduction: 25%25\%; Number needed to treat: 55
  5. E
    Relative risk reduction: 75%75\%; Number needed to treat: 55

Cevap

The relative risk reduction is 25%25\% and the number needed to treat is 2020.
The control event rate (CER) is 240/1,200=0.20240/1,200 = 0.20 (20%20\%), and the experimental event rate (EER) is 180/1,200=0.15180/1,200 = 0.15 (15%15\%). The relative risk reduction (RRR) is calculated as (CER−EER)/CER=(0.20−0.15)/0.20=0.25(CER - EER) / CER = (0.20 - 0.15) / 0.20 = 0.25, or 25%25\%. The absolute risk reduction (ARR) is CER−EER=0.20−0.15=0.05CER - EER = 0.20 - 0.15 = 0.05 (5%5\%). The number needed to treat (NNT) is the inverse of the absolute risk reduction (1/ARR1 / ARR), which is 1/0.05=201 / 0.05 = 20.

Adım Adım Çözüm

1
Calculate the event rate in both the control and intervention groups.
Control Event Rate (CER) = 240/1,200=0.20240 / 1,200 = 0.20 (20%20\%). Experimental Event Rate (EER) = 180/1,200=0.15180 / 1,200 = 0.15 (15%15\%).
Baseline risks are required to determine both absolute and relative measures of association.
2
Calculate the Relative Risk (RR) and Relative Risk Reduction (RRR).
RR=EER/CER=0.15/0.20=0.75RR = EER / CER = 0.15 / 0.20 = 0.75. RRR=1−RR=1−0.75=0.25RRR = 1 - RR = 1 - 0.75 = 0.25 (25%25\%).
RRR indicates how much the risk is reduced in the treatment group relative to the control group.
3
Calculate the Absolute Risk Reduction (ARR) and Number Needed to Treat (NNT).
ARR=CER−EER=0.20−0.15=0.05ARR = CER - EER = 0.20 - 0.15 = 0.05 (5%5\%). NNT=1/ARR=1/0.05=20NNT = 1 / ARR = 1 / 0.05 = 20.
NNT represents the number of patients who must be treated to prevent one additional adverse outcome and is the inverse of the ARR.

Anahtar Kavram

Calculation and differentiation of Relative Risk Reduction (RRR) and Number Needed to Treat (NNT)
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Konular

Measures of Association and Impact

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