A physician research group is evaluating the efficacy of a new lipid-lowering drug, Superstatin, which is being marketed directly to consumers as a groundbreaking new therapy to prevent heart attacks. The drug manufacturer claims that the drug is more effective than existing hypolipidemic agents for primary prevention of myocardial infarction. Results of a 5-year, randomized, double-blinded, controlled study to evaluate the efficacy of Superstatin are shown below. Compared to the control medication, how many patients need to be treated with Superstatin to prevent one additional myocardial infarction?

Question

A physician research group is evaluating the efficacy of a new lipid-lowering drug, Superstatin, which is being marketed directly to consumers as a groundbreaking new therapy to prevent heart attacks.  The drug manufacturer claims that the drug is more effective than existing hypolipidemic agents for primary prevention of myocardial infarction.  Results of a 5-year, randomized, double-blinded, controlled study to evaluate the efficacy of Superstatin are shown below.  Compared to the control medication, how many patients need to be treated with Superstatin to prevent one additional myocardial infarction?

Quizplus · Accepted Answer

11ec160b_370d_1be1_9249_b9d8990e2b09_MD0001_00 The number needed to treat (NNT) represents the number of patients that need to be treated with a medication (eg, Superstatin) in order to prevent an additional negative outcome (eg, myocardial infarction). NNT is calculated by dividing 1 by the absolute risk reduction (ARR). NNT = 1 / ARR ARR represents the actual difference in control and experimental group event rates. The data is not presented in the standard format of a contingency (2 × 2) table, so care should be exercised in selecting the appropriate values. In this example, the event of interest is myocardial infarction. There were 25 + 975 = 1,000 patients in the control group; of those, 25 had a myocardial infarction. Similarly, there were 10 + 990 = 1,000 patients in the treatment (ie, Superstatin) group; of those, 10 had a myocardial infarction. Therefore: Control event rate = 25 / 1,000 = 0.025 Experimental event rate = 10 / 1,000 = 0.01 ARR can then be calculated: ARR = Control event rate - Experimental event rate = 0.025 - 0.01 = 0.015, or 1.5% Finally, NNT is found by dividing 1 by 0.015: NNT = 1 / 0.015 = 66.6 ≈ 67 Rounding up the result to the nearest whole number, 67 patients need to be treated with Superstatin to prevent an additional myocardial infarction. The ideal NNT would be 1, meaning that all patients in the treatment group benefit from the treatment. A low NNT implies that a treatment is more beneficial because fewer patients need to be treated to prevent an additional negative outcome. For instance, if a third hypolipidemic medication had an NNT of 40, it would be more beneficial than Superstatin, as only 40 patients would need to be treated over a given period to prevent an additional myocardial infarction. Educational objective: The number needed to treat (NNT) is the number of patients that need to be treated with a medication to avoid an additional negative outcome. NNT is calculated by dividing 1 by the absolute risk reduction (the difference between the control and experimental group event rates). Lower NNT values represent more beneficial treatments.

A Physician Research Group Is Evaluating the Efficacy of a New