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Systematic Approach to Evidence-Based Medicine in Clinical Pharmacy Practice
Mary Roederer, PharmD, BCPS, CPP
Assistant Professor, Department of Family Medicine
Clinical Pharmacy Specialist in Family Medicine
Department of Pharmacy Services
University of North Carolina Hospitals
Chapel Hill, NC

Evidence-based medicine (EBM) is defined by many as "the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence-based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research."1 For many well-trained and experienced clinicians, EBM is the methodical appraisal occurring internally as they assess a patient and consider a treatment plan. As a clinical pharmacist, I define EBM as the systematic approach to evaluating clinical options for therapy and the way to "prove it" with regard to clinical recommendations. Early in my clinical practice, EBM gave me confidence in the recommendations I was making.

Overall, the application of EBM is very easy. The clinician considers the patient and his/her medical conundrum, evaluates the best clinical literature using a hierarchical approach to the available evidence, reviews the patient's specific values and desires, and applies the ultimate answer. At the outset, EBM evolved to manage the amassing evidence and teach the proper approach to learners (e.g., medical students/residents or pharmacy students/residents). However, the concept has grown to include pharmacoeconomic evaluations and medical guidelines. The original theory-to evaluate available literature properly and apply it to individual patient cases-may constrain the practice of medicine by assuming that every patient is the same.

The approach to using evidence-based medicine in clinical pharmacy practice is to develop a systematic approach to answering clinical conundrums. The very first step is to identify the clinical situation requiring more answers. Next, defining and refining the clinical question is essential. Without a clear, concise clinical question, it is difficult to find an expedient evidence-based answer. A broad question allows the search to be too expansive. A refined clinical question regarding the clinical situation allows for a reasonable search and limits the data to review. Performing a search yields all the relevant reviews or studies. In reviewing the search, the numbers are key ingredients. Evaluating the numbers gives credibility to the data and tangible elements of any discussion of the clinical question. Finally, integrating the patient's preferences or values provides the last component needed to achieve the ultimate answer.

The Systematic Approach

  1. Clinical Situation
  2. Clinical Question
  3. Search
  4. Evidence Review
  5. Numbers
  6. Clinical Answer
  7. Patient Preferences/Values
  8. Ultimate Answer

Let's look at an example of a systematic approach by considering the case of DF.

The Case of DF

Clinical Situation
DF is a 31-year old female with a history of migraines with an associated aura. She presents to her primary care physician (PCP) for a refill of her combined oral contraceptive. She is adamant that she must continue her contraceptive, as she is planning to be married in 1 month and does not wish to get pregnant at this time. Her PCP pages the clinical pharmacist to ask for advice.

Clinical Question
Is a history of migraine with aura a valid reason to avoid combined oral contraceptives?

A search for oral combined contraceptive and migraine with aura provides only four articles. None answer the clinical question. The search is changed to oral contraceptives and migraine with aura. Twenty-six articles are identified.

Evidence Review
The articles are individually reviewed. The best evidence is in a recent article in BMJ: "Risk of ischaemic stroke in people with migraine: systematic review and meta-analysis of observational studies."2 Several articles have abstracts but do not have links to full text. The articles without a full text link are not reviewed in their entirety. If one of the articles unavailable via a full text Internet link is the best evidence identified by abstract perusal, then the clinical pharmacist goes to a health sciences oriented library to read and copy the article for review. Although no guidelines are returned as part of the search, the clinical pharmacist is familiar with two relevant guidelines: The World Health Organization (WHO) recommends avoiding combined contraceptives in women with a history of migraine.3 Similarly, the American College of Obstetrics and Gynecology (ACOG) recommends alternate forms of contraception in women with a history of migraine with aura.4

According to this article, the relative risk of ischemic stroke in women with migraine who are taking oral contraceptives is 8.72 (5.05 to 15.05). The systematic review included observational, case-control, and cohort studies and requires further investigation.

Clinical Answer
The numbers suggest that the risk of ischemic stroke in migraineurs is greater in women who take oral contraceptives. In fact the risk is greater than eight times that of women without migraine or who do not take any oral contraceptives. Therefore DF should not be prescribed oral contraceptives.

Patient Preferences/Values
The patient understands the risk. She has taken oral contraceptives in the past. Her current situation requires a contraceptive. The patient does not have the time to evaluate all the options due to her upcoming wedding. She understands the importance of avoiding oral contraceptives. She will review the information provided by her PCP regarding intrauterine devices (IUDs) and return for a visit soon after her honeymoon.

Ultimate Answer
The PCP discusses the clinical evidence answer and the patient preferences with DF. DF chooses to begin the oral contraceptive, accepting the risk. She makes an appointment to return to her PCP 1 month after her wedding. They decide she will likely have an IUD placed at that time.

Although the systematic practice of using EBM to answer pertinent clinical questions appears simple, the approach is not without barriers. One barrier to EBM is that evidence-based guidelines, to help clinicians manage the growing evidence, are utilized by payors and regulatory agencies to limit practice. The tenet that every patient fits the guidelines is unreasonable. Many real-life patients are the types excluded from the available evidence due to comorbidities, inability to pay for service, or physical or mental limitations that decrease adherence to therapy.

A second barrier to EBM today is the Internet. Articles or studies unavailable or not accessible via the Internet may be the best evidence, but they are not reviewed as often. Time does not allow for clinicians to go to the library and copy the articles. Clinicians want the evidence at their fingertips. As a result, evidence-based resources and databases emerged to satisfy the growing need. However, a lag-time exists for integration into evidence-based resources and databases. Therefore, users of evidence-based databases should also perform a literature search to assure that no new evidence has emerged that would alter treatment decisions.

Overall, EBM is utilized more now than historically. Will all clinicians use EBM? Probably not. All clinicians completing any task or approaching any scenario the same is a strong assertion. With the ever-growing litigious environment for medicine in the United States, clinicians may choose to practice based on the evidence available, which may help the clinician in a liability suit. Many patients are not mirror images of the patients in the available evidence-and therein lies the problem. We have to look at each individual as a unique patient case. Can he or she afford the latest and greatest medication? Is a medication used as the gold-standard for 50 or more years no longer acceptable because a new medication has a better-quality study? Is a medication, such as warfarin for valvular atrial fibrillation stroke prevention appropriate for a patient unable to obtain international normalized ratios (INRs) due to immobility and care at home? Only time will tell which approach the medical community will take in embracing EBM. As a practicing clinical pharmacist, I will continue to use the available evidence to help me provide the best care for each patient presenting to my clinic.


  1. Sackett, D. Evidence-based Medicine - What it is and what it isn't. 1996.
  2. Etminam M, Takkouche B, et al. Risk of ischaemic stroke in people with migraine: systematic review and meta-analysis of observational studies. BMJ. 2005 Jan 8;330(7482):63.
  3. World Health Organization. Improving access to quality care in family planning: medical eligibility criteria for contraceptive use. 3rd edition. Geneva: World Health Organization, 2004.
  4. ACOG Practice Bulletin. The use of hormonal contraception in women with coexisting medical conditions. Int J Gynaecol Obstet. 2001; 75:93-106.

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