Pharmacy & Therapeutics - December 2008 - (Page 711)

Interpreting Estimates of Treatment Effects REFERENCES Number of wasted treatments (000) 100 80 60 40 20 0 0 5 10 15 Number needed to treat 20 Figure 3 Number of wasted treatments (in thousands) and the number needed to treat. Now let’s consider a health care system that treats 100,000 patients annually. Because we can compute the probability of a treatment failure, we can easily compute the number of wasted treatments as a function of the NNT. The results in Figure 3 indicate that treatment wastage increases dramatically as the NNT increases from one to five. For NNTs greater than five, treatment wastage is very high, but incremental increases in wastage are small with incremental increases in the NNT. Because effect magnitude measures have implications for wasted treatments, they also have implications for costs. If the costs of two treatments are identical, the treatment that leads to more wasted treatments would be more costly. If the treatments differ in cost, we would need to translate treatment wastage into treatment costs by multiplying the amount of waste by the cost. CONCLUSION Taking an evidence-based approach to patient care requires that health care professionals consider adverse events along with efficacy when they select treatments for their patients. This discussion of efficacy does not diminish the importance of the many other questions health care providers must consider when choosing treatments, such as: • Is the patient taking other treatments? • Does the patient have a coexisting disorder that suggests the need for combined pharmacotherapy? • Has the patient had a prior trial with any of the potential treatments? If so, what were the effects? These and other questions remind us that even though quantitative methods, such as the computation of effect magnitude, play a crucial role in the practice of evidence-based medicine, they will never fully replace the intellectual expertise of compassionate and informed health care professionals. Acknowledgment. Editorial assistance was provided by Health Learning Systems, part of CommonHealth. 1. Bucher HC, Guyatt GH, Griffith LE, Walter SD. The results of direct and indirect treatment comparisons in meta-analysis of randomized controlled trials. J Clin Epidemiol 1997;50(6):683–691. 2. Song F, Altman DG, Glenny AM, Deeks JJ. Validity of indirect comparison for estimating efficacy of competing inter ventions: Empirical evidence from published meta-analyses. BMJ 2003; 326(7387):472. 3. Chou R, Fu R, Huffman LH, Korthuis PT. Initial highly-active antiretroviral therapy with a protease inhibitor versus a nonnucleoside reverse transcriptase inhibitor: Discrepancies between direct and indirect meta-analyses. Lancet 2006;368(9546): 1503–1515. 4. Cook RJ, Sackett DL. The number needed to treat: A clinically useful measure of treatment effect. BMJ 1995;310(6977):452–454. 5. Cohen J. Statistical Power Analysis for the Behavioral Sciences, 2nd ed. Hillsdale, NJ: Erlbaum; 1988. 6. McGraw KO, Wong SP. A common language effect size statistic. Psychol Bull 1992;111:361–365. 7. Hanley JA, McNeil BJ. The meaning and use of the area under a receiver operating characteristic (ROC) curve. Radiology 1982; 143(1):29–36. 8. Colditz GA, Miller JN, Mosteller F. Measuring gain in the evaluation of medical technology: The probability of a better outcome. Int J Technol Assess Health Care 1988;4(4):637–642. 9. Faraone SV, Biederman J, Spencer TJ, Wilens TE. The drug– placebo response curve: A new method for assessing drug effects in clinical trials. J Clin Psychopharmacol 2000;20(6):673–679. 10. Kraemer HC, Kupfer DJ. Size of treatment effects and their importance to clinical research and practice. Biol Psychiatry 2006; 59(11):990–996. 11. Faraone SV, Biederman J, Spencer T, et al. Efficacy of atomoxetine in adult attention-deficit/hyperactivity disorder: A drug– placebo response curve analysis. Behav Brain Functions 2005;1(1):16. 12. Faraone S, Short E, Biederman J, et al. Efficacy of Adderall and methylphenidate in attention deficit hyperactivity disorder: A drug–placebo and drug–drug response curve analysis of a naturalistic study. Int J Neuropsychopharmacol 2002;5(2):121–129. 13. Faraone SV, Pliszka SR, Olvera RL, et al. Efficacy of Adderall and methylphenidate in attention-deficit/hyperactivity disorder: A drug–placebo and drug–drug response curve analysis. J Child Adolesc Psychopharmacol 2001;11(2):171–180. 14. Short EJ, Manos MJ, Findling RL, Schubel EA. A prospective study of stimulant response in preschool children: Insights from ROC analyses. J Am Acad Child Adolesc Psychiatry 2004;43(3): 251–259. 15. Tiihonen J, Hallikainen T, Ryynanen OP, et al. Lamotrigine in treatment-resistant schizophrenia: A randomized placebo-controlled crossover trial. Biol Psychiatry 2003;54(11):1241–1248. 16. Stata User’s Guide: Release 9. College Station, TX: Stata Corporation, LP; 2005. 17. Gale C, Oakley-Browne M. Generalised anxiety disorder. Clin Evid 2002(7):883–895. 18. Faraone SV, Biederman J, Spencer TJ, Aleardi M. Comparing the efficacy of medications for ADHD using meta-analysis. Medscape General Medicine e Journal 2006;8(4):4. 19. Faraone SV. Understanding the effect size of ADHD medications: Implications for clinical care. Medscape Psychiatry Mental Health 2003;8(2). 20. Geddes J, Butler R. Depressive disorders. Clin Evid 2002(7): 867–882. 21. Soomro GM. Obsessive compulsive disorder. Clin Evid 2002(7): 896–905. 22. Leucht S, Pitschel-Walz G, Abraham D, Kissling W. Efficacy and extrapyramidal side-effects of the new antipsychotics olanzapine, quetiapine, risperidone, and sertindole compared to conventional antipsychotics and placebo: A meta-analysis of randomized controlled trials. Schizophr Res 1999;35(1):51–68. I Vol. 33 No. 12 • December 2008 • P&T® 711

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Pharmacy & Therapeutics - December 2008 Contents Editorial Medication Errors Prescription: Washington New Drugs/Drug News/ New Medical Devices Drug Forecast Interpreting Estimates of Treatment Effects Chemotherapy Foundation Symposium XXVI: Innovative Cancer Therapy for Tomorrow Third Annual Onmark National Payor/Provider Forum Fourth Annual Ophthalmic Drug Development and Delivery Summit Classification and Pharmacological Management Of Obesity CE Test and Forms Season’s Greetings: Thanks to Our Readers and Reviewers

Pharmacy & Therapeutics - December 2008

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