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Difficulty: MediumMedical Literature and Drug Advertisement Interpretation

A physician is reviewing a promotional pamphlet for a newly approved oral hypoglycemic agent. The pamphlet includes a safety summary comparing the incidence of severe hypoglycemic episodes between the new medication and placebo over a 52-week clinical trial period.

The safety data excerpt reports the following:
- Novel Agent Group (N=4,000N = 4,000): 180 patients experienced at least one episode of severe hypoglycemia.
- Placebo Group (N=4,000N = 4,000): 112 patients experienced at least one episode of severe hypoglycemia.

Based on the clinical trial data provided in the promotional material, how many patients must be treated with the novel agent instead of placebo for 52 weeks to expect one additional severe hypoglycemic event? (Round your final answer to the nearest whole number).

Answer: 59 patients

Answer

59
The Number Needed to Harm (NNH) is derived from the Absolute Risk Increase (ARI). The ARI is the difference between the Experimental Event Rate (EER) and the Control Event Rate (CER). In this trial, the EER is 180/4000=0.045180/4000 = 0.045 and the CER is 112/4000=0.028112/4000 = 0.028. The difference (ARI) is 0.0170.017. The NNH is calculated by taking the reciprocal of the ARI (1/0.0171/0.017), which equals 58.8258.82. Rounding to the nearest whole number yields 5959 patients.

Step-by-Step Solution

1
Calculate the Experimental Event Rate (EER).
EER=1804000=0.045EER = \frac{180}{4000} = 0.045 (or 4.5%4.5\%)
To determine the absolute risk of the adverse event in the population receiving the new intervention.
2
Calculate the Control Event Rate (CER).
CER=1124000=0.028CER = \frac{112}{4000} = 0.028 (or 2.8%2.8\%)
To determine the baseline absolute risk of the adverse event in the control population.
3
Calculate the Absolute Risk Increase (ARI).
ARI=EER−CER=0.045−0.028=0.017ARI = EER - CER = 0.045 - 0.028 = 0.017 (or 1.7%1.7\%)
To find the excess risk of the adverse event directly attributable to the new medication.
4
Calculate the Number Needed to Harm (NNH).
NNH=1ARI=10.017≈58.82NNH = \frac{1}{ARI} = \frac{1}{0.017} \approx 58.82
NNH indicates how many patients need to be exposed to the risk factor over a specific period to cause one additional harmful event.
5
Round the final value to the nearest whole number.
5959
Clinical metrics representing whole patients cannot be expressed as fractions, and standard rounding rules apply.

Key Concept

The Number Needed to Harm (NNH) quantifies the safety of an intervention and is calculated as the inverse of the Absolute Risk Increase (NNH=1/ARINNH = 1 / ARI).
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Topics

Medical Literature and Drug Advertisement Interpretation

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