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Evidence-Based Medicine Guide

A Library Guide to Evidence-Based Medicine

Types of Clinical Questions

Clinical questions may be categorized as either background or foreground. Why is this important?

Determining the type of question will help you to select the best resource to consult for your answer.

Background questions ask for general knowledge about an illness, disease, condition, process or thing. These types of questions typically ask who, what, where, when, how & why about things like a disorder, test, or treatment, etc.

For example

  • How overweight is a woman to be considered slightly obese?
  • What are the clinical manifestations of menopause?
  • What causes migraines?

Foreground questions ask for specific knowledge to inform clinical decisions. These questions typically concern a specific patient or particular population. Foreground questions tend to be more specific and complex compared to background questions. Quite often, foreground questions investigate comparisons, such as two drugs, two treatments, two diagnostic tests, etc. Foreground questions may be further categorized into one of 4 major types: treatment/therapy, diagnosis, prognosis, or etiology/harm.

For example

  • Is Crixivan effective in slowing the rate of functional impairment in a 45 year old male patient with Lou Gehrig's Disease?
  • In pediatric patients with Allergic Rhinitis, are Intranasal steroids more effective than antihistamines in the management of Allergic Rhinitis symptoms?

Constructing a Well Built Clinical Question

According to Centre for Evidence Based Medicine (CEBM),"One of the fundamental skills required for practising EBM is the asking of well-built clinical questions. To benefit patients and clinicians, such questions need to be both directly relevant to patients' problems and phrased in ways that direct your search to relevant and precise answers".

A well-built clinical foreground question should have 4 components. The PICO model is a helpful tool that assists you in organizing and focusing your foreground question into a searchable query. Dividing into the PICO elements helps identify search terms/concepts to use in your search of the literature.

P = Patient, Problem, Population

  • How would you describe a group of patients similar to you?
  • What are the most important characteristics of the patient or population?
  • What is the condition or disease you are interested in?

I = Intervention, Prognostic Factor, Exposure

  • What main intervention are you considering?
  • What do you want to do with this patient (e.g. treat, diagnose, observe)?

C = Comparison (Can be None or Placebo)

  • What is the main alternative to compare with the intervention?
  • Are you trying to decide between two drugs, a drug and no medication or placebo, or two diagnostic tests?

O = Outcome

  • What are you trying to accomplish, measure, improve or affect?

Type of Clinical Question and Study Design

Two additional important elements of the well-built clinical question to consider are the type of foreground question and the type of study (methodology). This information can be helpful in focusing the question and determining the most appropriate type of evidence.

Foreground questions can be further divided into questions that relate to therapy, diagnosis, prognosis, etiology/harm.

Therapy: Questions of treatment in order to achieve some outcome. May include drugs, surgical intervention, change in diet, counseling, etc.
Diagnosis: Questions of identification of a disorder in a patient presenting with specific symptoms.
Prognosis: Questions of progression of a disease or likelihood of a disease occurring.
Etiology/Harm: Questions of negative impact from an intervention or other exposure.

Knowing the type of foreground question can help you select the best study design to answer your question. You always want to look for the study design that will yield the highest level of evidence. Consult the pyramid and the definitions below.

EBM Pyramid & EBM Page Generator from Dartmouth College and Yale

Definitions of Study Types
From the British Medical Journal’s Clinical Evidence Glossary

Systematic Reviews: a review in which specified and appropriate methods have been used to identify, appraise, and summarize studies addressing a defined question. It can, but need not, involve meta-analysis). In Clinical Evidence, the term systematic review refers to a systematic review of RCTs unless specified otherwise.

Critically-Appraised Topics: evaluates and synthesizes multiple research studies.

Critically-Appraised Individual Articles: critically-appraised individual articles evaluates and provides a synopsis of individual research studies.

Randomized Controlled Trials: a trial in which participants are randomly assigned to two or more groups: at least one (the experimental group) receiving an intervention that is being tested and another (the comparison or control group) receiving an alternative treatment or placebo. This design allows assessment of the relative effects of interventions.

Cohort Studies: a non-experimental study design that follows a group of people (a cohort), and then looks at how events differ among people within the group. A study that examines a cohort, which differs in respect to exposure to some suspected risk factor (e.g. smoking), is useful for trying to ascertain whether exposure is likely to cause specified events (e.g. lung cancer). Prospective cohort studies (which track participants forward in time) are more reliable than retrospective cohort studies.

Case Control Studies: a study design that examines a group of people who have experienced an event (usually an adverse event) and a group of people who have not experienced the same event, and looks at how exposure to suspect (usually noxious) agents differed between the two groups. This type of study design is most useful for trying to ascertain the cause of rare events, such as rare cancers.

Case Series / Case Reports: analysis of series of people with the disease (there is no comparison group in case series).

Background Information / Expert Opinion: Evidence in these resources may vary from expert opinion to high levels of evidence.