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Evidence Based Medicine

Origins

The minireview on the scientific method of investigation dealt mainly with individual studies. There is another level of concern when we look at review articles that attempt to synthesize the results of multiple studies, especially when there may be disparate results. The goals of the best of these reviews are to assist in achieving the conscientious, specific, and logical use of current best evidence in making decisions about the care of individuals. This is known as evidence-based medicine (). The practice of evidence-based medicine blends individual clinical expertise of the caregiver with the best available clinical evidence from systematic research.

The concept of evidence-based medicine is said to have had its origins in mid 19th century Paris or maybe even earlier.

There are 5 steps in practicing evidence-based medicine (Centre for Evidence Based Medicine). They are:

Asking clinical questions that can be answered.
Finding (uncovering) the best evidence
Critically evaluating the evidence
Applying the evidence
Evaluating the results

Clinicians face an enormous task of trying to keep pace with all the medical advances published in primary journals. In fact, one estimate in 1996 suggested that a typical clinician has less than one hour a week to devote to reading journals (). Unfortunately, the quality of many studies and published information is not uniform which makes the task orders of magnitude more difficult. So, trying to find the best evidence can be extremely difficult. Furthermore, there are inherent problems with applying the evidence in evidence-based medicine ().

The available data usually from randomized controlled trials (RCTs) or meta-analyses do not include many types of treatments or patients seen in clinical practice.
Treatment is usually presented for the average study patient. Clinical features including symptom severity and additional problems (co-morbidity) are often not addressed in the data presentation.
RCTs are usually not available for concerns about diagnosis, etiology, or prognosis.
RCTs seldom provide enough information to make ongoing clinical decisions that are influenced by pathophysiological changes that occur with treatment.
Patient’s psychosocial factors and support, and personal preferences are usually not reflected in published results.

Further, when making a clinical diagnosis based upon the frequency of clinical features found in patients with the disease, it is critical to determine the validity and applicability of available research ().

For validity, one needs to know

how the diagnosis was verified,
how the sample of patients in the study relates to all of the patients who have the disease,
how the clinical findings were determined, and
how these findings were characterized.

As to applicability:

of course, one needs to consider if these criteria apply to their patient, and
if newly published research has superseded these criteria.

Tools and Sources

One tool to help physicians is the clinical decision rule (CDR). CDRs attempt to formally test, simplify and increase accuracy of diagnostic and prognostic assessments (). They are clinical tools that quantify for a particular disease, the individual contributions that constituents of the history, physical examination, and laboratory results make in clinical assessments. CDRs may guide clinicians, indicate pretesting probability for diagnosis, point out screening tests for common problems, and estimate risk. Level 1 CDRs are one’s that have been validated in a new clinical setting and are most likely to help reduce costs while enhancing quality of care and patient satisfaction.

To try to fill the gap, new evidence based medicine journals have sprung up, and two important sources of information that meet the highest standards for validity have come into existence. They are the Agency for Healthcare Research and Quality (AHRQ) and the Cochrane Collaboration.

Since 1999, the AHRQ formerly known as the Agency for Health Care Policy and Research has been the lead Federal agency on quality-of-care research. Its sister agencies include the National Institutes of Health, the Centers for Disease Control, and the Food and Drug Administration. It coordinates all Federal quality improvement efforts and health services research. It supports the development of evidence-based reports through its 12 Evidence-based Practice Centers and the dissemination of evidence-based guidelines through the AHRQ’s National Guideline Clearinghouse. It provides a wealth of information on relevant health care issues to both health care professionals and health consumers. Their web site is http://www.ahrq.gov. Its overall goal is to improve the use and quality of healthcare, reduce its cost, and enhance access to services.

Since 1992, there has been a new gold standard in systematic scientific reviews. It is called the Cochrane Collaboration. The Cochrane Collaboration is an international organization that helps people to make well-informed decisions about health care. They do this by preparing, maintaining, and ensuring access to systematic reviews of the effects of health care interventions. There are no better medical publications for scientific rigor. Their reviews are published electronically in the Cochrane Database of Systematic Reviews.

The Cochrane Collaboration maintains other databases that also make searching for the best evidence much easier. One of these databases is the Evidence-Based Medicine Guidelines (EBMG). It combines clinical guidelines with documentation of regularly updated scientific evidence. Short summaries based on the best evidence from systematic reviews in the Cochrane Library and other reliable sources are designed to keep the user updated in the latest evidence-based information without the need for extensive reading. This can be a real boon for the overworked physician. Annual subscriptions are remarkably low priced and are available on line from Joanne@update.co.uk.

One of the important services provided by the Cochrane Collaboration is the Cochrane Controlled Trials Register (CCTR). Its mission is to search the world’s health care journals and other sources of information to create an unbiased source of information for systematic reviews. It is collaborating in this endeavor with the National Library of Medicine who produce Medline, and Reed Elsevier who produce Embase (www.nlm.nih.gov/services/cochrane.html).

Of special interest to us in the application of psychoneuroimmunology is the validity of psychological interventions to boost immune responses. So, it is fitting that we conclude this brief article with considerations of how to evaluate that evidence base. A powerful review of psychological therapies for cancer patients () has produced an excellent summary of recommendations to improve the validity of RCTs. Their 10 indicators for quality of the trials are points that an astute reader of scientific articles should keep in mind. To paraphrase them:

Has the study ensured that subjects have been randomly allocated, and eligibility assessed before allocation to experimental groups?
Are the subjects randomly selected from a defined population, or are all eligible subjects consecutively selected in a given time frame?
Have the subjects been blinded to their experimental group?
Have the care providers been blinded to the subject’s experimental group? However, this is not possible in some instances such as with psychotherapy.
Have usual care practices been maintained without change for the duration of the study for the control group?
Have the caregivers been thoroughly trained and tested to ensure adherence to the study protocols?
Have measures been instituted to decrease the number of subjects lost to follow-up?
Has the study provided detailed loss to follow up information?
If there is loss-to-follow up, has the study conducted intention-to-treat analyses?
Has the study used objective measures, or if only subjective measures were feasible, have they ensured study outcomes were measured in a way that was blinded to subject’s experimental groups?

For more on quality control in science, please refer to Psychoneuroimmunology for the Health Sciences.

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