An Evidence-Based Clinical Mystery
The Bedford Murder is intended for health care professionals. First and foremost this book is about evidence. It is a murder mystery and the evidence must be considered to determine who-done-it it also models the process of Evidence- Based Medicine(EBM) in clinical practice; and finally it is a book of evidence-based clinical pearls. It is about critical appraisal, clinical practice, and entertainment all rolled into one.
And it works!
PREFACE
For those not familiar with the process of incorporating Evidence Based Medicine into practice, the book models the five steps of EBM: i) asking a clinical question, ii) finding sources of information to answer the question, iii) critically appraising that information, iv) making a practice decision based on the critically appraised evidence, v) and then reflecting, after a period of time, on the effect of that practice decision.
The book is based on clinical cases presenting to a family doctors office. It deals with diabetes, hypertension, depression, oral contraception, tennis elbow, urinary tract infections, gastro-esophageal reflux and much more. The clinical pearls are evidence-based, succinct, and pertinent. And spun through the book is a story, a murder mystery. The main character is a young family doctor who is intent on finding out why one of her patients has suddenly disappeared. The disappearance is affecting many of the patients in her practice, especially the missing manís family members. A fishing trip, a love affair from the past, and two families of some means who are linked by marriage but with little else in common, all play a part. As the clues mount, the family doctor, as well as the reader, try to determine from the evidence just what is going on.
Each clinical encounter in this book is followed by a number of clinical questions which arise from it. We (the authors) have done a detailed literature search to identify the best evidence to answer these questions, but the reader needs to consider what other information or evidence he or she is aware of, and from which sources, that might also be used to help answer the questions. We have critically appraised the articles we are citing and have come to conclusions based on the evidence, as we see it. Readers need to decide if they agree. Perhaps the conclusions we arrive at are inappropriate for the context of the reader’s clinical practice. We have made decisions about how the family doctor in the book applied the evidence to her clinical situation. Readers should decide whether they agree with this and whether they would apply the results in the same way or a different way. It is useful to recognize that there are five types of clinical questions asked in this book.
They are questions of diagnosis, therapy, harm, prognosis, and etiology.
Diagnosis questions are about factors or tests that help with diagnosis. These tests may be laboratory or imaging investigations, but they may also be features on history and physical examination. Generally sensitivity and specificity are addressed. They may be studies that look at the accuracy of a rapid screening test for diagnosing a specific condition. Generally the test is compared to a gold standard. (EG: when determining how well the urine dipstick test detects urinary tract infection, its accuracy would be compared to the gold standard of a urine culture. Or a diagnosis may ask how accurately the presence of green sputum on history predicts the presence of pneumonia on chest xray).
Therapy questions are about the effectiveness of therapy. They may be about a drug or a non-pharmacological therapy. Generally these questions ask about the value of a treatment at decreasing symptoms, curing a disease, preventing further morbidly, or decreasing mortality.
Harm questions are about the potential for harmful effects of drugs or other treatments or the potential for harmful effects of diagnostics tests. They may also relate to the potentially harmful effects of environmental substances on disease but here the boundary between etiology and harm begins to blur. In this book the questions of harm generally refer to harmful effects of treatments or diagnostic tests.
Prognosis questions relate to the ability to predict the outcome of a given disease or condition based on certain features of the disease or of the individual. Perhaps men, who
smoke, and are hypertensive may be more likely to die within 5 years of contracting a certain condition then are women who do not smoke and are not hypertensive.
Etiology questions are about factors that are causally related to the development of a specific condition or disease. Does stress cause this condition? Which bacteria are most likely to cause infection in this location? This type of question can be similar to a question about harm.
There are number of types of research studies that may be conducted to answer the different types of questions. Depending on the methodology used these studies can be ranked based on the strength of their design and their ability to accurately answer the type of question. This has led to a concept of Levels of Evidence whereby (for questions of therapy, harm, and etiology) well done randomized controlled trials are considered to produce be very high levels of evidence and case-series studies to produce a significantly lower level of evidence. Expert opinion that is not based on good research is the lowest level of evidence of all.
We used a ‘real-life’ approach in the book; that is we asked the clinical question and then went in search of the evidence rather than finding a good article and concocting a clinical scenario around it. There are many sources and types of information or ‘evidence’ randomized controlled trials, cohort studies, case-control studies, studies evaluating the sensitivity and specificity of a test, or descriptive studies to name a few. These are different types of studies providing evidence of varying quality. Many times the best available evidence was of low quality. So we used whatever evidence and information we could find to provide the best care to the patient.
Marshall Godwin MD CCFP
Geoffrey Hodgetts MD CCFP