Randomised controlled trials should be the basis for developing clinical guidelines and for decisions about individual patient management. They should also inform public health policy. However, their capacity to fulfil these roles will depend on how closely a trial’s participants reflect the general population of patients with the disorder that has been investigated. The extent to which a trial’s findings are relevant to the broader population of patients with the disorder is referred to as the trial’s generalisability, or external validity. The CONSORT statement refers to generalisability under Item 21 (Box 1).1 Well-written reports should discuss the various factors that influence the generalisability of the trial’s findings. Julian and Pocock have proposed a checklist of questions to assist with this assessment (see Box 2).2
The full article is accessible to AMA members and paid subscribers. Login to read more or purchase a subscription now.
Please note: institutional and Research4Life access to the MJA is now provided through Wiley Online Library.
- 1. Moher D, Schulz KF, Altman DG. The CONSORT statement: revised recommendations for improving the quality of reports of parallel-group randomised trials. Lancet 2001; 357: 1191-1194.
- 2. Julian DG, Pocock SJ. Interpreting a trial report. In: Pitt B, Julian D, Pocock S, editors. Clinical trials in cardiology. London: Saunders; 1997.
- 3. Bonadonna G, Brusamolino E, Valagussa P, et al. Combination chemotherapy as an adjuvant treatment in operable breast cancer. N Engl J Med 1976; 294: 405-410.
- 4. Bonadonna G, Valagussa P. Chemotherapy of breast cancer: current views and results. Int J Radiat Oncol Biol Phys 1983, 9: 279-297.
- 5. Langlands AO, Tiver KW. Adjuvant chemotherapy in breast cancer [letter]. Int J Radiat Oncol Biol Phys 1984, 10: 943-946.
- 6. Evans A, Kalra L. Are the results of randomized controlled trials on anticoagulation in patients with atrial fibrillation generalizable to clinical practice? Arch Intern Med 2001; 161: 1443-1447.
- 7. Stroke Prevention in Atrial Fibrillation (SPAF) Investigators. Stroke Prevention in Atrial Fibrillation study: final results. Circulation 1991; 84: 527-539.
- 8. Yuasa H, Kurita K, Westesson P-L. External validity of a randomized clinical trial of temporomandibular disorders: analysis of the patients who refused to participate. Br J Oral Maxillofacial Surg 2003; 41: 129-131.
- 9. Bahit MC, Cannon CP, Antman M, et al. Direct comparison of characteristics, treatment, and outcomes of patients enrolled versus patients not enrolled in a clinical trial at centers participating in the TIMI 9 trial and TIMI 9 registry. Am Heart J 2003; 145: 109-117.
- 10. Moore DAJ, Goodall RL, Ives NJ, et al. How generalizable are the results of large randomized controlled trials of retroviral therapy? HIV Med 2000; 1: 149-154.
- 11. Scandinavian Simvastatin Survival Study Group. Randomised trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian Simvastatin Survival Study (4S). Lancet 1994; 344: 1383-1389.
- 12. LIPID Study Group. Prevention of cardiovascular events and death with pravastatin in patients with coronary heart disease and a broad range of initial cholesterol levels. N Engl J Med 1998; 339: 1347-1357.
- 13. Heart Protection Study Collaborative Group. MRC/BHF Heart Protection Study of cholesterol lowering with simvastatin in 4963 people with diabetes: a randomised placebo-controlled trial. Lancet 2003; 361: 2005-2016.
- 14. Lord SJ, Gebski VJ, Keech AC. Multiple analyses in clinical trials: sound science or data dredging? Med J Aust 2004; 181: 452-454.
- 15. Horton R. Common sense and figures: the rhetoric of validity in medicine: Bradford Hill Memorial Lecture 1999. Stat Med 2000; 19: 3149-3164.
We thank Rhana Pike for expert assistance in preparation of this manuscript.
None identified.