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Zorluk: KolayMeasures of Association and Impact

A randomized, double-blind, placebo-controlled trial is conducted to evaluate the efficacy of a novel lipid-lowering medication in preventing myocardial infarction in high-risk patients. A total of 2,000 patients are enrolled and equally randomized to receive either the new medication or a placebo. Over a 5-year follow-up period, 50 out of the 1,000 patients in the treatment group experience a myocardial infarction. In the placebo group, 100 out of the 1,000 patients experience a myocardial infarction. Based on these findings, what is the number needed to treat with the new medication to prevent one additional myocardial infarction over 5 years?

  1. A
    2
  2. B
    10
  3. 20Cevap
  4. D
    50
  5. E
    100

Cevap

20
The correct answer is 20 because the Number Needed to Treat (NNT) is the inverse of the Absolute Risk Reduction (ARR). The ARR is the control event rate (100/1000=0.10100/1000 = 0.10) minus the experimental event rate (50/1000=0.0550/1000 = 0.05), which equals 0.050.05. Therefore, NNT=1/0.05=20NNT = 1 / 0.05 = 20.

Adım Adım Çözüm

1
Calculate the Control Event Rate (CER).
CER=100/1000=0.10CER = 100 / 1000 = 0.10 (or 10%10\%).
This establishes the baseline risk of the outcome occurring without the new intervention.
2
Calculate the Experimental Event Rate (EER).
EER=50/1000=0.05EER = 50 / 1000 = 0.05 (or 5%5\%).
This determines the risk of the outcome occurring when the patient receives the new intervention.
3
Calculate the Absolute Risk Reduction (ARR).
ARR=CER−EER=0.10−0.05=0.05ARR = CER - EER = 0.10 - 0.05 = 0.05 (or 5%5\%).
ARR represents the absolute difference in risk between the control and experimental groups.
4
Calculate the Number Needed to Treat (NNT).
NNT=1/ARR=1/0.05=20NNT = 1 / ARR = 1 / 0.05 = 20.
NNT is the reciprocal of the absolute risk reduction, indicating how many patients need the treatment to prevent one bad outcome.

Anahtar Kavram

The Number Needed to Treat (NNT) is calculated as 1/ARR1 / ARR, where Absolute Risk Reduction (ARR) is the difference between the control event rate and the experimental event rate.
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Measures of Association and Impact

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