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Difficulty: EasyMedical Literature and Drug Advertisement Interpretation

A medical resident is presenting a recent multicenter, randomized controlled trial at journal club. The trial evaluated a novel medication, neprastatin, for the prevention of acute exacerbations in patients with severe chronic obstructive pulmonary disease (COPD). The study enrolled 5,000 patients, with 2,500 randomly assigned to receive daily neprastatin and 2,500 assigned to receive a placebo. At the end of the 2-year follow-up period, the published abstract states that 150 patients in the placebo group experienced an acute COPD exacerbation, compared to 100 patients in the neprastatin group.

Based on the results presented in the abstract, what is the number needed to treat (NNT) with neprastatin to prevent one acute COPD exacerbation?

Answer: 50 patients

Answer

50
To calculate the Number Needed to Treat (NNT), one must first find the Absolute Risk Reduction (ARR). The Control Event Rate (CER) is the risk of the event in the placebo group: 150/2500=0.06150 / 2500 = 0.06 (or 6%6\%). The Experimental Event Rate (EER) is the risk of the event in the intervention group: 100/2500=0.04100 / 2500 = 0.04 (or 4%4\%). The ARR is the difference between these two rates: CER−EER=0.06−0.04=0.02CER - EER = 0.06 - 0.04 = 0.02. The NNT is the inverse of the ARR (1/ARR1 / ARR), which evaluates to 1/0.02=501 / 0.02 = 50. This means 50 patients must be treated with neprastatin to prevent one acute COPD exacerbation.

Step-by-Step Solution

1
Identify the number of events and total patients in each group from the abstract.
Placebo group: 150 events out of 2,500 patients. Neprastatin group: 100 events out of 2,500 patients.
These values are required to calculate the event rates for both the control and experimental groups.
2
Calculate the Control Event Rate (CER).
CER=1502500=0.06CER = \frac{150}{2500} = 0.06
CER represents the baseline risk of the event occurring without the new intervention.
3
Calculate the Experimental Event Rate (EER).
EER=1002500=0.04EER = \frac{100}{2500} = 0.04
EER represents the risk of the event occurring with the new intervention.
4
Calculate the Absolute Risk Reduction (ARR).
ARR=CER−EER=0.06−0.04=0.02ARR = CER - EER = 0.06 - 0.04 = 0.02
ARR measures the absolute difference in risk between the two groups.
5
Calculate the Number Needed to Treat (NNT).
NNT=1ARR=10.02=50NNT = \frac{1}{ARR} = \frac{1}{0.02} = 50
NNT is defined as the inverse of the ARR.

Key Concept

Number Needed to Treat (NNT) calculation from clinical trial data
Estimated Time:1m 0s
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Topics

Medical Literature and Drug Advertisement Interpretation

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