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9 - Quantifying treatment effects using randomized trials

Published online by Cambridge University Press:  04 August 2010

Thomas B. Newman  and
Michael A. Kohn
Thomas B. Newman
Affiliation:
University of California, San Francisco
Michael A. Kohn
Affiliation:
University of California, San Francisco
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Summary

Introduction

As we noted in the Preface and Chapter 1, because the purpose of doing diagnostic tests is often to decide whether or how to treat the patient, we may need to quantify the effects of treatment to decide whether to do a test. For example, if the treatment for a disease provides a dramatic benefit, we should have a lower threshold for testing for that disease than if the treatment is of marginal or unknown efficacy. In this chapter, we discuss how to quantify the effects of treatments using the results of randomized trials. In Chapter 10, we will extend the discussion to observational studies of treatment efficacy.

In a randomized trial, study participants are randomly assigned to treatment groups, and the groups are compared to determine which had better outcomes. We begin by briefly reviewing the reasons to do randomized trials, then discuss their critical appraisal. Our approach is somewhat eclectic. Our goal is to highlight issues most important for obtaining and interpreting estimates of treatment effects, not to review the entire topic of randomized trials, and our selection is based partly on issues that seem to have received insufficient attention elsewhere.

We conclude this chapter with a discussion of calculating the treatment cost per bad outcome prevented, a rough step forward in the process of quantifying risks and benefits of treatments.

Type
Chapter
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Evidence-Based Diagnosis , pp. 186 - 205
Publisher: Cambridge University Press
Print publication year: 2009

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Hollis, S., and Campbell, F. (1999). “What is meant by intention to treat analysis? Survey of published randomised controlled trials.” Br Med J 319(7211): 670–4.CrossRefGoogle ScholarPubMed
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Nissen, S. E., Tsunoda, T., et al. (2003). “Effect of recombinant ApoA-I Milano on coronary atherosclerosis in patients with acute coronary syndromes: a randomized controlled trial.” JAMA 290(17): 2292–300.CrossRefGoogle ScholarPubMed
Russell, S. (2003). Drug cuts risk of breast-cancer relapse. Chronicle. San Francisco, CA. Oct 10, Page l.Google Scholar
Tonstad, S., Tonnesen, P., et al. (2006). “Effect of maintenance therapy with varenicline on smoking cessation: a randomized controlled trial.” JAMA 296(1): 64–71.CrossRefGoogle ScholarPubMed
Treanor, J. J., Hayden, F. G., et al. (2000). “Efficacy and safety of the oral neuraminidase inhibitor oseltamivir in treating acute influenza: a randomized controlled trial. US Oral Neuraminidase Study Group.” JAMA 283(8): 1016–24.CrossRefGoogle ScholarPubMed
Waksman, R., Ajani, A. E., et al. (2002). “Intravascular gamma radiation for in-stent restenosis in saphenous-vein bypass grafts.” N Engl J Med 346(16): 1194–9.CrossRefGoogle ScholarPubMed
Welliver, R., Monto, A. S., et al. (2001). “Effectiveness of oseltamivir in preventing influenza in household contacts: a randomized controlled trial.” JAMA 285(6): 748–54.CrossRefGoogle ScholarPubMed

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