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July 19, 2000

Assessing Prevention Interventions by "Number Needed to Treat"

Author Affiliations

Stephen J.LurieMD, PhD, Contributing EditorIndividualAuthor

JAMA. 2000;284(3):303-305. doi:10.1001/jama.284.3.303

To the Editor: We agree with Dr Kumana and colleagues1 that NNT is useful to assess the effectiveness of medical therapies. Although the authors briefly mentioned the importance of evaluating treatments relative to other "indicated drug interventions," they did not provide comparisons of the NNTs from statin trials to the NNTs of other commonly accepted preventive therapies. It is important, however, to discuss the NNT compared with the overall cardiovascular risk of the study population, because the NNT in a primary prevention trial usually is much higher than in a secondary prevention trial due to the lower absolute cardiovascular event rates. The NNTs from primary prevention of cardiovascular disease trials in middle-aged patients are listed in Table 1.

Table. Number Needed to Treat (NNT) From Trials
of Primary Prevention of Cardiovascular Disease*
Table. Number Needed to Treat (NNT) From Trials of Primary Prevention of Cardiovascular Disease*

Kumana et al do not indicate what the appropriate NNT should be to consider a preventive therapy effective. These data demonstrate that using lipid-lowering therapy for the primary prevention of cardiovascular events in middle-aged patients has an NNT as good as or better than that for treatment of hypertension, diabetes mellitus, and other preventive therapies for such diseases as osteoporosis (data not shown), if used in patients with at least 1 cardiovascular risk factor in addition to hypercholesterolemia. The NNTs for primary prevention with lipid-lowering medications are similar to those observed in secondary prevention trials, such as the Scandinavian Simvastatin Survival Study, the Cholesterol and Recurrent Events Study, and the Long-term Intervention with Pravastatin in Ischemic Disease Study.1

Kumana  CRCheung  BMYLauder  IJ Gauging the impact of statins using number needed to treat.  JAMA. 1999;282:1899-1901.Google Scholar
Owns  JRClearfield  MWeis  S  et al.  Primary prevention of acute coronary events with lovastatin in men and women with average cholesterol levels: results of AFCAPS/TexCAPS.  JAMA. 1998;279:1615-1628.Google Scholar
Shepard  JCobbe  SMFord  I  et al. for the West of Scotland Coronary Prevention Study Group, Prevention of coronary heart disease with pravastatin in men with hypercholesterolaemia.  N Engl J Med. 1995;333:1301-1307.Google Scholar
West of Scotland Coronary Prevention Group, West of Scotland Coronary Prevention Study: identification of high-risk groups and comparison with other cardiovascular intervention trials.  Lancet. 1996;348:1339-1342.Google Scholar
Frick  MHElo  OHaapa  K  et al.  Helsinki Heart Study: primary prevention trial with gemfibrozil in middle-aged men with dyslipidemia.  N Engl J Med. 1987;317:1237-1245.Google Scholar
Medical Research Council Working Party, Medical Research Council trial of treatment of hypertension in older adults: principal results.  BMJ. 1992;304:405-412.Google Scholar
UK Prospective Diabetes Study (UKPDS) Group, Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34).  Lancet. 1998;352:854-865.Google Scholar