A 59-year-old man comes to the office for follow-up. He has a history of hypertension for which he takes 2 antihypertensive agents. The patient has no other cardiovascular problems and does not smoke. On examination, his blood pressure is 145/90 mm Hg and BMI is 25.4 kg/m². The remainder of the examination is unremarkable. Laboratory studies show elevated fasting lipid levels, including LDL cholesterol. His 10-year risk of cardiovascular events is calculated as 10%, and a discussion regarding moderate or intensive statin therapy is initiated. The patient has read that statins may cause diabetes and asks if there is an even more increased risk with intensive compared to moderate statin therapy.
Based on the abstract results with regard to incident diabetes, what is the approximate number needed to harm over 1 year for intensive compared to moderate statin therapy?

Question

Quizplus · Accepted Answer

Explanation: If exposure is associated with increased risk of disease, the number needed to harm (NNH) can indicate how many patients need to be exposed before a harmful event occurs in 1 patient. NNH is the inverse of the absolute risk increase (ARI), which is the difference in incidence rate between the exposed and non-exposed groups. ARI is sometimes referred to as attributable risk. number needed to harm (NNH) In this meta-analysis, intensive statin therapy corresponds to the exposed group and moderate statin therapy corresponds to the non-exposed group. The incidence of diabetes was increased in the exposed group (risk of 18.9 cases per 1000 exposed patient-years) compared to the non-exposed group (risk of 16.9 cases per 1000 non-exposed patient-years). ARI = (18.9/1000 - 16.9/1000) = 2/1000 = 0.002 per person per year Therefore, NNH = 1/ARI = 1/0.002 = 500 This means that 500 patients would need to receive intensive statin therapy for a year before 1 patient develops diabetes (would not have occurred on moderate statin therapy). If exposure is beneficial (decreased risk of disease), the number needed to treat (NNT)determines the number of patients who need to be exposed (eg, treated with an intervention) to prevent 1 bad outcome. NNT is the inverse of the absolute risk reduction (ARR). For instance, intensive statin therapy was associated with a decreased risk of major cardiovascular events (44.5 versus 51.6 per 1000 patient-years), so ARR = (51.6/1000 - 44.5/1000) = 7.1/1000 = 0.0071. Therefore, NNT = 1/0.0071 = 140 (Choice D). Data are not always presented in the standard 2 × 2 format seen above, so care should be taken when applying memorized formulae. In addition, using the values listed under the table (1449 out of 16408 and 1300 out of 16344) will lead to the incorrect answer as these values refer to the overall number of cases over the course of the entire trial (which lasted >1 year), whereas the question asks for NNH over 1 year. (Choices A and B) In this case, 2/1000 and 7/1000 (not 2 and 7) represent the ARI and ARR, respectively. Educational objective: The number needed to harm (NNH) is a measure that indicates how many patients need to be exposed to a particular risk factor over a specific period before a harmful event occurs in 1 patient. NNH is the inverse of the absolute risk increase (or attributable risk), which is the difference in incidence rate between exposed and non-exposed patients.

A 59-Year-Old Man Comes to the Office for Follow-Up