Number needed to treat: analyzing of the effectiveness of thoracoabdominal aortic repair

European Journal of Vascular and Endovascular Surgery : the Official Journal of the European Society for Vascular Surgery
C C MillerHazim J Safi

Abstract

Number needed to treat (NNT) is a method used to calculate the number of patients who need to be treated to prevent one adverse outcome. To analyze the effectiveness of thoracoabdominal and descending thoracic aortic aneurysm repair, we computed the NNT required to prevent one death. Between Jan 1991 and Feb 2003, we repaired 1004 aneurysms of the descending thoracic and thoracoabdominal aorta. We followed the patients from surgery until death. Five-year actuarial survival in our population was computed by the Kaplan-Meier method. Natural history data for comparison were taken from the population-based work of Bickerstaff et al., 1982. NNT was calculated as the reciprocal of the risk difference at 5 years. 95% confidence intervals were computed by the method of Daly. Five-year mortality in the population-based cohort was 87 vs. 39% in our treated population, for a risk difference of 48%. 1/0.48=2, indicating that two patients need to be treated to prevent one death at 5 years (95% CI 1.8-2.5, p<0.0001). An NNT of two demonstrates the effectiveness of surgical repair of descending thoracic and thoracoabdominal aortic aneurysms when compared to the natural history. By comparison, carotid endarterectomy for symptomatic lesions >70...Continue Reading

References

May 1, 1997·Annals of Internal Medicine·H J McQuay, R A Moore
Aug 1, 1997·European Journal of Vascular and Endovascular Surgery : the Official Journal of the European Society for Vascular Surgery·H J SafiP J Asimacopoulos
Apr 29, 1998·American Journal of Epidemiology·L E Daly
Nov 4, 1998·The Annals of Thoracic Surgery·H J SafiJ C Baldwin
Nov 7, 1998·BMJ : British Medical Journal·D G Altman
Mar 13, 2003·British Journal of Clinical Pharmacology·Yoon Kong LokeSheena Derry

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