Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘ConclusionThis chapter provides an introduction to three statistical methods commonly usedto assess the effects of intervention and risk factors on medical outcomes.Multivariate analysis is a very powerful tool in medical research that helps us tounderstand the multidimensional nature of risk factors of diseases and how theseare interlinked.The choice of analysis method depends on the form of the response variable:linear regression is used to analyze continuous responses, logistic regression forbinary data, and hazards regression for survival times. Table 4 briefly summarizesthe basic assumptions and the interpretation of results from these three separatemultiple regression methods. A common thread of these applications is to identifyand control for possible confounding factors through multivariate analysis. Thisallows us to understand whether an association is independently important ofother factors. More about the use of multiple regression methods can be found inKatz’s book [7].References1. Llewellyn-Jones RH, Baikie KA, Smithers H, et al. Multifaceted shared care interventionfor late life depression in residential care: randomised controlled trial. BMJ 1999;319:676–82.2. Eagle KA, Goodman SG, Avezum A, et al. for the GRACE Investigators. Practice variationand missed opportunities for reperfusion in ST-segment-elevation myocardial infarction: findingsfrom the Global Registry of Acute Coronary Events (GRACE). Lancet 2002;359:373–7.3. Taneja AK, Collinson J, Flather MD, et al. Mortality following non-ST elevation acute coronarysyndrome: 4 years follow up of the PRAIS UK Registry (Prospective Registry of Acute IschaemicSyndromes in the UK). Eur Heart J 2004;25:2013–18.4. Wei M, Gibbons LW, Mitchell TL, et al. Low fasting plasma glucose level as a predictorof cardiovascular disease and all-cause mortality. Circulation 2000;101:2047–52.5. Pocock SJ, McCormack V, Gueyffier F, et al. A score for predicting risk of death fromcardiovascular disease in adults with raised blood pressure, based on individual patient datafrom randomised controlled trials BMJ 2001;323:75–81.6. Budoff MJ, Diamond GA, Raggi P, et al. Continuous probabilistic prediction of angiographicallysignificant coronary artery disease using electron beam tomography. Circulation 2002;105:1791–6.7. Katz MH. Multivariable Analysis: A Practical Guide for Clinicians. Cambridge, UK; New York:Cambridge University Press, 1999.285