The benefits and pitfalls of evidence-based medicine

Abstract

A major benefit of evidence-based medicine is that it allows obtaining information about treatment, most difficult to get empirically. In addition, it provides information about the side effects of new drugs, not known at the time they were approved for clinical practice. Cardiol ogy is a specialty making the most of data of evidence-based medicine, that is, information derived from prospective, randomized, double-blind controlled trials focusing on "hard" endpoints such as modulation of morbidity and mortality. Data emerging from costly prospective studies of morbidity and mortality substantially extend and improve our therapeutic options, while the outcomes of studies should not be taken for granted. Studies resulting in disappointment include those showing low efficacy of vasopeptidase inhibitors, cytokine antagonists, or endothelin receptor antagonists in the treatment of chronic heart failure. Evidence-based medicine also allows obtaining information about the risks associated with some treatments. Pitfalls o f evidence-based medicine include the fact patients in prospective randomized blind studies are usually less ill that those in clinical practice. Patients are usually younger. The rates of concomitant disease are also lower compared with clinical practice. In some trials, patients represent just a fraction of those screened. Hence, the conclusions drawn from these studies are not applicable to all patients, including those excluded from the study. In addition, pat ients in clinical studies are on closer follow-up compared with patients in clinical practice, as stipulated by study protocols requiring more frequent and more thorough laboratory investigations. Another pitfall of prospective double-blind studies is some may select an inferior sparring partner. Yet another problem may be the reluctance of journals or sponsors to disclose negative outcomes of studies. When interpreting studies, it is imperative to consider inclusion and exclusion criteria. It is impossible to extrapolate positive results to patients not monitored in the study in question. The fact that antihype rtensive therapy reduces cerebrovascular and coronary morbidity and mortality as well as the incidence of heart failure has been recognized for 35 years. The fact that therapy is also required for isolated systolic hypertension of the elderly, and that treatment will appreciably improve the prognosis of these patients, has been known for 10-15 let. Still, hypertension control is not satisfactory in the Czech Republic and worldwide, and is referred to as No. 1 cardiovascular scandal. Those to be blamed for poor control of hypertension include both physicians (inadequately aggressive therapy) and patients (poor adherence to therapy due to inadequate motivation). Cardiovascular scandal No. 2, in the eyes of British physicians, is the current status of lipid-lowering therapy with statins. While statins are often not used to treat high-risk patients with CHD, they are frequently given to patients with an overall low cardiovascular risk. The standard of management of chronic heart failure by general practitioners and in hospitals is likewise unsatisfactory. Regrettably, the influence of evi dence-based medicine is smaller than one would wish to be, and not only in this country, as prescription is affected by many other powerful factors such as marketing tools, fringe benefits, and others. How could one otherwise explain the high prescription rates of classes of drugs not supported by a single study? Company leaflets are not untrue, they just tell the truth in 95%, or even less.