Numbers needed to treat derived from meta-analyses---sometimes informative, usually misleading

BMJ 1999;318:1548-1551 ( 5 June )

Education and debate

Numbers needed to treat derived from meta-analyses $---$ sometimes informative, usually misleading

Liam Smeeth, research fellow ^a, Andy Haines, professor of primary care ^a, Shah Ebrahim, professor of epidemiology and ageing ^b.

^a Department of Primary Care and Population Sciences, Royal Free and University College Medical School, University College London, London NW3 2PF, ^b MRC Health Services Research Collaboration, Department of Social Medicine, University of Bristol, Bristol BS8 2PR

Correspondence to: Professor Ebrahim shah.ebrahim@bristol.ac.uk

The first 150 words of the full text of this article appear below.

The number needed to treat $---$ the number of patients who must be treated to prevent one adverse outcome $---$ is a widely used measure. ¹ ² It is increasingly being calculated by pooling absolute risk differencesin trials included in meta-analyses. ³ ⁴ This option is availablein statistical software and the Cochrane Database of SystematicReviews. ⁵ ⁶ In this paper, we examine pooled numbers neededto treat derived from trials and meta-analyses of interventionsto prevent cardiovascular disease. We show that a pooled numberneeded to treat may be misleading because of variation in theevent rates in trials, differences in the outcomes considered,effects of secular trends on disease risk, and differences inclinical setting. The number needed to treat should be derivedby applying the relative risk reductions from treatment whichhave been estimated by trials or meta-analysis to relevant baselinerisks for different types of patients. This provides a range of. . . [Full text of this article]

CiteULike

Complore

Connotea

Del.icio.us Add to Digg

Digg

StumbleUpon Add to Technorati

Technorati What's this?

This article has been cited by other articles:

Nelson, H. D., Tyne, K., Naik, A., Bougatsos, C., Chan, B. K., Humphrey, L. (2009). Screening for Breast Cancer: An Update for the U.S. Preventive Services Task Force. ANN INTERN MED 151: 727-737 [Abstract] [Full text]
Loke, Y. K. MBBS MD, Singh, S. MD MPH, Furberg, C. D. MD PhD (2009). Long-term use of thiazolidinediones and fractures in type 2 diabetes: a meta-analysis. CMAJ 180: 32-39 [Abstract] [Full text]
McAlister, F. A. MD MSc (2008). The "number needed to treat" turns 20 -- and continues to be used and misused. CMAJ 179: 549-553 [Full text]
Schmelzle, J., Rosser, W. W., Birtwhistle, R. (2008). Update on pharmacologic and nonpharmacologic therapies for smoking cessation. cfp 54: 994-999 [Abstract] [Full text]
Buckley, P. F., Foster, A., Miller, B. (2008). Schizophrenia Host Vulnerability and Risk of Metabolic Disturbances During Treatment with Antipsychotics. Focus 6: 172-179 [Abstract] [Full text]
Currow, D. C., Abernethy, A. P. (2006). Frameworks for Approaching Prescribing at the End of Life. Arch Intern Med 166: 2404-2404 [Full text]
Bongartz, T., Sutton, A. J., Sweeting, M. J., Buchan, I., Matteson, E. L., Montori, V. (2006). Anti-TNF antibody therapy in rheumatoid arthritis and the risk of serious infections and malignancies: systematic review and meta-analysis of rare harmful effects in randomized controlled trials.. JAMA 295: 2275-2285 [Abstract] [Full text]
Costa, J., Borges, M., David, C., Vaz Carneiro, A. (2006). Efficacy of lipid lowering drug treatment for diabetic and non-diabetic patients: meta-analysis of randomised controlled trials. BMJ 332: 1115-1124 [Abstract] [Full text]
Barnes, M L, Lipworth, B J, Weatherall, M, Masoli, M, Beasley, R (2006). Clinical importance of the Step 3 choice in asthma. Thorax 61: 180-181 [Full text]
Wen, L., Badgett, R., Cornell, J. (2005). Number needed to treat: A descriptor for weighing therapeutic options. Am J Health Syst Pharm 62: 2031-2036 [Abstract] [Full text]
Madan, R., Bhatia, A., Chakithandy, S., Subramaniam, R., Rammohan, G., Deshpande, S., Singh, M., Kaul, H. L. (2005). Prophylactic Dexamethasone for Postoperative Nausea and Vomiting in Pediatric Strabismus Surgery: A Dose Ranging and Safety Evaluation Study. Anesth. Analg. 100: 1622-1626 [Abstract] [Full text]
Nordmann, A. J, Hengstler, P., Leimenstoll, B. M, Harr, T., Young, J., Bucher, H. C (2004). Clinical outcomes of stents versus balloon angioplasty in non-acute coronary artery disease: A meta-analysis of randomized controlled trials. Eur Heart J 25: 69-80 [Abstract] [Full text]
Beich, A., Thorsen, T., Rollnick, S. (2003). Screening in brief intervention trials targeting excessive drinkers in general practice: systematic review and meta-analysis. BMJ 327: 536-542 [Abstract] [Full text]
Marx, A., Bucher, H. C (2003). Numbers needed to treat derived from meta-analysis: a word of caution. Evid. Based Med. 8: 36-37 [Full text]
Leung, G. M., Lam, T.-H., Thach, T. Q., Hedley, A. J. (2002). Will Screening Mammography in the East Do More Harm than Good?. AJPH 92: 1841-1846 [Abstract] [Full text]
Barrowman, N. J. (2002). Missing the point (estimate)? Confidence intervals for the number needed to treat. CMAJ 166: 1676-1677 [Full text]
Lee, A., Gin, T. (2002). Applying the Results of Quantitative Systematic Reviews to Clinical Practice. Anesth. Analg. 94: 372-377 [Full text]
Schachter, H. M., Pham, B., King, J., Langford, S., Moher, D. (2001). How efficacious and safe is short-acting methylphenidate for the treatment of attention-deficit disorder in children and adolescents? A meta-analysis. CMAJ 165: 1475-1488 [Abstract] [Full text]
Ciliska, D., Cullum, N., Marks, S. (2001). Evaluation of systematic reviews of treatment or prevention interventions. Evid. Based Nurs. 4: 100-104 [Full text]
Ebrahim, S. (2001). The Use of Numbers Needed to Treat Derived from Systematic Reviews and Meta-Analysis: Caveats and Pitfalls. Eval Health Prof 24: 152-164 [Abstract]
, , , , , , , , , , , , , E., , , , R., , G., , , , , , , , , , M, , , , R. (2001). Do not resuscitate. BMJ 322: 102-102 [Full text]
Tonkin, A. M (2000). GENERAL CARDIOLOGY: Evaluation of large scale clinical trials and their application to usual practice. Heart 84: 679-684 [Full text]
Heller, R. F, Dobson, A. J, Smeeth, L., Ebrahim, S. (2000). Disease impact number and population impact number: population perspectives to measures of risk and benefit Commentary: DINS, PINS, and things---clinical and population perspectives on treatment effects. BMJ 321: 950-953 [Full text]
Figueredo, E., Sadhasivam, S., Saxena, A., Kathirvel, S., Kannan, T. R. (2000). Ondansetron and Evidence-Based Medicine Response. Anesth. Analg. 91: 496-497 [Full text]
Clemenson, N. D., Ebrahim, S., Smith, G. D., LaRosa, J. C. (2000). Statins and Risk of Coronary Heart Disease. JAMA 283: 2935-2935 [Full text]
Cates, C., Delaney, B., Moayyedi, P., Soo, S., Deeks, J., Forman, D., Pantoflickova, D, Blum, A L, Talley, N J, Koelz, H R, McNamara, D., Buckley, M, O'Morain, C, Jaakkimainen, L., Boyle, E., Tudiver, F. (2000). Will eradication of Helicobacter pylori improve symptoms of non-ulcer dyspepsia?. BMJ 320: 1208a-1208 [Full text]
Charlton, B. G, Hopayian, K., McGough, J., D'Amico, R., Deeks, J. J, Altman, D. G, Moore, A., McQuay, H. (1999). Numbers needed to treat derived from meta-analysis. BMJ 319: 1199a-1199 [Full text]

Rapid Responses:

Read all Rapid Responses

NNT - not necessarily true: Bruce G Charlton
bmj.com, 9 Jun 1999 [Full text]
At odds with reality: Stephen Senn
bmj.com, 8 Jun 1999 [Full text]
NNTs are tools - use them appropriately: Andrew Moore, et al.
bmj.com, 14 Jun 1999 [Full text]
NNTs from patient-years too can mislead: Kevork Hopayian
bmj.com, 18 Jun 1999 [Full text]
Poor reporting of length of follow-up in clinical trials and systematic reviews: Roberto D'Amico, et al.
bmj.com, 25 Jun 1999 [Full text]