A state health department conducts a retrospective cohort analysis to evaluate the safety of a new targeted biologic therapy for moderate-to-severe plaque psoriasis. The investigators specifically monitor the incidence of herpes zoster reactivation over a 3-year follow-up period, comparing patients on the new biologic therapy to a separate cohort receiving traditional systemic agents.
The study results are summarized in the following table:
| Treatment Group | Total Patients | Herpes Zoster Cases |
|---|---|---|
| Targeted biologic therapy | 2,500 | 175 |
| Traditional systemic agents | 4,000 | 120 |
Assuming these results are statistically significant, what is the number needed to harm (NNH) for the targeted biologic therapy compared to traditional systemic agents?
- A4
- B14
- 25Cevap
- D33
- E55
Cevap
25
The number needed to harm (NNH) represents the number of patients who must be exposed to a risk factor or medication over a specified period to cause one additional adverse event. It is calculated mathematically as the inverse of the Absolute Risk Increase (). To find the ARI, first determine the incidence of the adverse event in both groups. The incidence in the targeted biologic group is (7%). The incidence in the traditional systemic agents group is (3%). The ARI is the difference between these two rates (). The NNH is therefore . This indicates that for every 25 patients treated with the targeted biologic therapy instead of traditional agents, one additional case of herpes zoster reactivation will occur.
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The Number Needed to Harm (NNH) is calculated as the inverse of the Absolute Risk Increase (ARI). It requires calculating the incidence rates for both exposed and unexposed groups, finding their difference, and taking the inverse.
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