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Figure 1. 
Evidence to support clinical decisions. Stat indicates statistically; sig, significant; nonsig, nonsignificant; and RCT, randomized controlled trial.

Evidence to support clinical decisions. Stat indicates statistically; sig, significant; nonsig, nonsignificant; and RCT, randomized controlled trial.

Figure 2. 
The results of Ellis et al and ours at Ottawa General Hospital (OGH), Ottawa, Ontario, according to the classification of Ellis et al. RCTs indicates randomized controlled trials.

The results of Ellis et al6 and ours at Ottawa General Hospital (OGH), Ottawa, Ontario, according to the classification of Ellis et al. RCTs indicates randomized controlled trials.

Diagnoses and Therapies Provided for Which Placebo–Randomized Controlled Trials Existed
Diagnoses and Therapies Provided for Which Placebo–Randomized Controlled Trials Existed
Original Investigation
August 10/24, 1998

Are Therapeutic Decisions Supported by Evidence From Health Care Research?

Author Affiliations

From the Department of Internal Medicine, Ottawa General Hospital/University of Ottawa, Ottawa, Ontario.

Arch Intern Med. 1998;158(15):1665-1668. doi:10.1001/archinte.158.15.1665

Background  One of the most common decisions physicians face is deciding which therapeutic intervention is the most appropriate for their patients. In recent years much emphasis has been placed on making clinical decisions that are based on evidence from the medical literature. Despite the emphasis on incorporation of evidence-based medicine into the undergraduate curriculum and postgraduate medical training programs, there has been controversy regarding the proportion of interventions that are supported by health care research.

Objective  To investigate the proportion of major therapeutic interventions at our institution that are justified by published evidence.

Methods  One hundred fifty charts from the internal medicine department were reviewed retrospectively. The main diagnosis, therapy provided, and patient profile were identified and a literature search using MEDLINE was performed. A standardized search strategy was developed with high sensitivity and specificity for identifying publication quality. The level of evidence to support each clinical decision was ranked according to a predetermined classification. In this system there were 6 distinct levels, which are explained in the study.

Results  Of the decisions studied, 20.9% could be supported by placebo-controlled randomized trials and 43.9% by head-to-head trials. Half of these were shown to be significantly superior to the treatment against which it was being compared. For 10 of the 150 clinical decisions, evidence was found demonstrating alternative therapies as being more effective than that selected.

Conclusions  Most primary therapeutic clinical decisions in 3 general medicine services are supported by evidence from randomized controlled trials. This should be reassuring to those who are concerned about the extent to which clinical medicine is based on empirical evidence. This finding has potential for quality assurance, as exemplified by the discovery that a literature search could have potentially improved these decisions in some cases.

IN RECENT years much emphasis has been placed on making clinical decisions based on evidence from the medical literature. Evidence-based medicine (EBM) is an approach to medical practice that encourages the use of the results of health care research as a component of clinical decision making. The use of these results complements physicians' clinical experience and knowledge of basic sciences. There has been widespread interest in this approach, and EBM has been integrated into the undergraduate and postgraduate programs at many medical schools, including the University of Ottawa in Ottawa, Ontario.

Physicians are often faced with deciding which therapeutic intervention is the most appropriate for their patients. In a small study1 from the Ottawa General Hospital, 37% of physicians surveyed stated that the primary reason for conducting a literature search was to assist in selection of the most effective drug therapy for his/her patient. This is consistent with the Rochester Study,2 which found that 45% of physicians based their choice of drugs on information from a literature search. The test of this approach is whether clinical decisions actually made in the care of patients are based on evidence, ie, justified by good studies.

Major discrepancies exist regarding the percentage of interventions supported by high-quality evidence from health care research. Before 1995 a commonly quoted estimate of interventions supported by good evidence was 10% to 20%. This figure, albeit widely cited, probably originates from the results of a British study by Forsyth3 in 1963. This estimate was derived from the prescribing practices of 19 family physicians in a northern industrial town in England over a nonconsecutive 2-week period. They examined the diagnosis and therapeutic intent of the medications prescribed. It was found that only 9.3% of proprietary drugs were specific for the diagnosis. This value has been subsequently cited in addresses to the Office of Technology Assessment of the US Congress, challenging audiences to provide evidence to the contrary.4,5 In an article published in 1995, Ellis and colleagues6 chronicled the decision-making patterns of a medical team. This study assessed whether the treatments given for the primary diagnoses for 109 inpatients were based on evidence. Their finding was that evidence from randomized controlled trials (RCTs) accounted for 53% of treatment decisions; convincing nonexperimental evidence for 29%; and interventions without substantial evidence for 18% of these decisions. Overall, it was found that 82% of patients were judged by the investigators' criteria to have received evidence-based interventions. This article evoked considerable debate about the generalizability of these results, so we decided to assess whether these higher estimates held true for internal medicine in a medical center in North America.

The goal of our study was to assess what proportion of clinical therapy decisions in our institution are supported by the best available evidence from the health care literature. Our institution was also interested in the potential for using this as a strategy for quality assurance, since documentation that the care provided is based on the latest scientific evidence has intrinsic appeal for the public, the patients, and the health care providers. Another goal of the study was to assess the potential impact of high-quality studies available from the medical literature on clinical decision making.


Our study used a retrospective review of a systematic sample of charts of patients admitted to the Clinical Teaching Unit (CTU) at the Ottawa General Hospital, a university hospital in Ottawa, a mid-sized Canadian city. The CTU consists of 3 general medicine teams, each composed of a staff member, a senior resident, 1 or 2 junior residents, and 1 or more senior medical students. Patients' charts for all admissions on 2 preselected days per month for a 1-year period (June 1994-June 1995) were reviewed. For any patient readmitted with the same diagnosis, only the initial hospital admission was included within the study results. A standardized data abstraction form was developed and used to record (1) the most responsible diagnosis, (2) the major therapeutic maneuver (extracted from the discharge summary as dictated by the physician directly caring for the patient), (3) patient population characteristics, and (4) the desired outcome. Disease categories were defined by subcategories as outlined in the International Classification of Diseases, Ninth Revision (ICD-9).7 The OVID 3.0 version of MEDLINE from January 1966 to June 1995 was used to conduct the search for the best evidence, using a modification of the search strategy from Haynes et al8; the search started with the most recent databases and was discontinued once all databases were searched or an article was retrieved containing a statistically and/or clinically significant placebo-controlled RCT supporting the use of the intervention used by the team. A checklist was developed that captured the key methodological elements recommended by Guyatt et al9 and by Sackett et al.10 This differed from the scale used by Ellis et al6 in 2 respects; first, the information collected included an assessment of the statistical power (β≤0.20) to ensure that the trials were sufficiently large to draw a valid conclusion; second, we distinguished between observational study designs that had control groups (cohort or case-control designs) from simple case series without controls. The articles are classified based on the quality level of the evidence. Levels are the following:

  • Statistically significant placebo-RCTs (low α error, P ≤.05)

  • Nonsignificant placebo-RCTs

  • Statistically significant head-to-head trials (low α error, P≤.05)

  • Nonsignificant head-to-head trials

  • Case-control and cohort studies

  • Case series without control subjects

  • No supporting evidence retrieved

Primary analysis comprised descriptive statistics of disease classification and related therapy(ies). With a sample size of 150 patients, and a hypothesized estimate of 20% of clinical decisions being based on statistically and clinically significant placebo-RCTs, the 95% confidence interval ranges from 14% to 26%.

To compare the results obtained at our institution with those from the study by Ellis et al,6 the charts were then reviewed and classified according to the 3 following levels: (1) interventions without substantial evidence, (2) convincing nonexperimental evidence, and (3) evidence from RCTs. Physician experts in the appropriate subspecialty who were blinded to the chart review and its hypothesis were charged with reviewing each case and classifying it according to the above-mentioned classification.


Of 150 charts selected for review, 148 met the inclusion criteria. The remaining 2 cases were patients already enrolled in the study and were consequently readmitted for the same diagnosis. To demonstrate the generalizability of the types of questions posed at our center, the decisions for which statistically significant placebo-RCTs were retrieved are presented as a sample in Table 1. The data collected were categorized according to the expanded classification schema described earlier. These results are presented in Figure 1.

Of 148 cases analyzed, 31 of the clinical decisions could be supported by a placebo-RCT demonstrating a clinically important and statistically significant (P≤.05) benefit over placebo. The remaining 3 clinical trials showed no statistical benefit over placebo for that specific diagnosis even though the statistical power was adequate.

In 65 of the cases the major intervention, although not tested in a placebo-controlled trial, was supported by a head-to-head trial (65 [43.9] of the references retrieved). Thirty-three of these showed one intervention to be statistically superior over the therapy to which it was being compared and the drug of choice was used in all 33 of these cases. In the remaining 32 cases no statistical advantage was demonstrated between the 2 treatment arms. In 28 of these cases the therapy chosen by the CTU was the standard therapy that constituted the control arm in these studies. Case-control or cohort studies included 23 (15.5%) of these studies. Case series accounted for 4 (2.7%) of those located. Cases for which no study was found to support the intervention accounted for the remaining 22 (14.7%).

In 10 cases (6.7%) an alternate therapy was identified from a controlled trial that was clinically and statistically superior to that chosen. This subgroup includes cases from all levels. Examples from this group include (1) giving omeprazole alone for peptic ulcer disease11; (2) prescribing pyrazinamide alone for tuberculosis12; and (3) using amino glutethimide for Cushing disease rather than ketoconazole.13

As stated earlier, to allow for comparison of results with the study by Ellis et al,6 our group classified the results of this study according to their classification. These results are given in Figure 2. As may be seen, the results were similar to those obtained by Ellis and colleagues. In 57% of cases in this study, the evidence to support the decisions made could be supported by RCTs, either placebo controlled or head to head, compared with 53% in the study by Ellis et al. Our group classified 27% of the decisions made by our CTU as convincing nonexperimental evidence. This result was also in keeping with the results of 29% by Ellis et al. Finally, interventions without substantial evidence were found to encompass 16% of CTU decisions in this study, compared with 18% in the study by Ellis et al.


The results of this study demonstrate that most clinical decisions made in the CTUs at our institution were supported by the best available evidence from health care research and positively support those found by Ellis et al.6 The robustness of this result is strengthened because this involved assessment of the best available evidence to support therapy decisions made by the 24 different teams studied. In addition, it aids to refute the misperception that a significant proportion of clinical decisions made by physicians may be erroneous and/or hazardous.

The generic ability of this result is limited by the fact that it was carried out at an internal medicine teaching service in a university hospital setting. Thus, this study needs to be repeated in different disciplines and settings before generalizing the results to other groups and sites. However, at the hospital where this study was performed, the CTU admits more than 95% of its patients from the emergency department that provides care to the local community; most patients are admitted to internal medicine and the patients admitted have diagnoses common to the practice of internal medicine anywhere in the world, as can be seen from Table 1.

Evidence-based medicine has limitations like most things in medicine. There exist ethical problems conducting placebo-controlled long-term studies; large sample sizes are needed to detect rare adverse effects and the effects of comorbidities cannot be assessed in most trials. We acknowledge that there remains a necessity to obtain nonexperimental studies in the absence of RCTs in the setting of decisions dealing with rare conditions and those not ethically amenable to RCT methodology.

However, there is consensus on the use of being able to show that a clinical decision is supported by documented benefit as demonstrated in a methodologically sound study. Although we accept that "not all that is measured is of value, and not all that is valued can be measured,"14 critical appraisal skills are essential if physicians are to be able to interpret and integrate the scientific basis of medicine where it exists. The ability to detect clinically important and statistically sound studies is a skill that can be acquired by clinicians who are not trained to carry out research themselves. In this age of increasing consumerism, patients have a right to expect their clinician to provide them with quantitative estimates of benefit and risk. Critical appraisal skills are fundamental if the evidence is to be presented in a balanced fashion, using data sources such as the Cochrane Collaboration Library.15

Our study also has application in the area of quality assurance. We believe that quality assurance in the provision of optimal care to our patients is provided by ensuring that our clinical decisions have been informed by health care research whenever possible. The fact that such a large proportion of care studied is indeed justifiable on the basis of sound research is a powerful argument for its incorporation into quality assurance programs. The finding that a literature search could have potentially improved on these decisions in some cases further supports its justification as a powerful tool in quality assurance programs. Furthermore, it can help clinicians avoid being pressed by their patients into making clinical decisions based on the latest media headline or Web site on the Internet, which the patient has obtained from the now widely accessible consumer health information. As there are no means of quality assurance for these sources of information, they may evoke clinical decisions made without foundation. The avoidance of decisions based on unfounded benefit may be potentially health and cost saving, and therefore should appeal to those individuals or establishments paying for health care, clinicians, and the general public. Such an assurance strategy also links the evaluation of health care to the curriculum and role modeling by the teachers in university training institutions. Health outcomes are certainly the final truth, and can be usefully applied as a trigger to examine conditions in detail where the outcomes vary excessively in internal medicine from local or national norms.

In conclusion, the widespread use of EBM, a scientific approach to clinical decision making, as a component of clinical practice may be of benefit to both the clinician and his/her patient. However, to date the exact value of this method on clinical decision making is yet unmeasured. The ultimate success of EBM as a therapeutic tool is contingent on continuous faculty and student development. This priority has been identified in initiatives such as the Educating Future Physicians for Ontario (EFPO) Project16 and the CANMEDS 2000 Project of the Royal College of Physicians and Surgeons of Canada.17

Corresponding author: Peter Tugwell, MD, MSc, FRCPC, Department of Medicine, University of Ottawa, 501 Smyth Rd, Ottawa, Ontario, Canada K1H 8L6.

Accepted for publication January 8, 1998.

Michaud  GMcGowan  JLvan der Jagt  RDugan  ATugwell  P Evidence-based medicine as a component of daily practice.  Bull Med Libr Assoc. 1996;84478- 481Google Scholar
Marshall  JG The impact of hospital library on clinical decision making: The Rochester Study.  Bull Med Libr Assoc. 1992;80169Google Scholar
Forsyth  G An inquiry into the drug bill.  Med Care. 1963;110- 16Google ScholarCrossref
Office of Technology Assessment of the US Congress, The Impact of RCTs on Health Policy and Medical Practice.  Washington, DC US Government Printing Office1983;
Office of Technology Assessment of the US Congress, Assessing the Efficacy and Safety of Medical Technologies.  Washington, DC US Government Printing Office1978;
Ellis  JMulligan  IRowe  JSackett  D Inpatient general medicine is evidence based.  Lancet. 1995;346407- 410Google ScholarCrossref
World Health Organization, International Classification of Diseases, Ninth Revision (ICD-9).  Geneva, Switzerland World Health Organization1977;
Haynes  RWilczynski  NMcKibbon  KWalker  CSinclair  J Developing optimal search strategies for detecting clinically sound studies in MEDLINE.  J Am Med Inform Assoc. 1994;1447- 457Google ScholarCrossref
Guyatt  GSackett  DCook  DEvidence-Based Medicine Working Group, Users' guides to the medical literature, II: how to use an article about therapy or prevention, B—what were the results and will they help me in caring for my patients?  JAMA. 1994;27159- 63Google ScholarCrossref
Sackett  DHaynes  RGuyatt  GTugwell  P Clinical Epidemiology: A Basic Science for Clinical Medicine.  Boston, Mass Little Brown & Co Inc1991;
Labenz  JGyenes  ERuhl  GBorsch  G Amoxicillin plus omeprazole versus triple therapy for eradication of Helicobacter pylori in duodenal ulcer disease: a prospective, randomized, and controlled study.  Gut. 1993;341167- 1170Google ScholarCrossref
Okwera  AWhalen  CByekwaso  F  et al.  Randomized trial of thiacetazone and rifampicin-containing regimens for pulmonary tuberculosis in HIV-infected Ugandans.  Lancet. 1994;3441323- 1328Google ScholarCrossref
Engelhardt  DWeber  M Therapy of Cushing's syndrome with steroid biosynthesis inhibitors.  J Steroid Biochem Mol Biol. 1994;49261- 267Google ScholarCrossref
Bradley  FField  J Evidence-based medicine.  Lancet. 1995;346830Google Scholar
The Cochrane Collaboration, The Cochrane Database of Systematic Reviews.  The Cochrane Library [book on CD-ROM]. Oxford, England The Cochrane Collaboration1996;Google Scholar
Neufeld  VR Demand-side medical education: educating future physicians for Ontario.  CMAJ. 1993;1481471- 1477Google Scholar
Turnbull  JM The role of general internal medicine in the spectrum of medical education.  R Coll Physicians Surg Can. 1996;29146- 149Google Scholar