• Why do we need evidence?
• What is evidence?
• What counts as evidence?
• Where do we find evidence?
Why do we need evidence?
• Commercial companies
We used to be certain about
• Blood letting
• Grommets for “glue ear”
• Lignocaine to prevent cardiac arrest post heart attack
• Egg white and Oxygen to heal pressure sores
• Vigorous rubbing of the buttocks with alcohol to prevent pressure sores
• 10 out of ten improve
• What about the 11th
What is evidence?
• a thing or things helpful in forming a conclusion or judgment
• that which tends to prove or disprove something; ground for
• something that makes plain or clear; an indication or sign
What counts as evidence?
• The outcome of systematic enquiry
• Meta-analysis is a statistical procedure that integrates the
results of several independent studies considered to be
• Well conducted meta-analyses allow a more objective
appraisal of the evidence than traditional narrative reviews,
provide a more precise estimate of a treatment effect, and
may explain heterogeneity between the results of individual
• Ill conducted meta-analyses, on the other hand, may be
biased owing to exclusion of relevant studies or inclusion of
Relationship between systematic reviews and meta-analyses
Regression towards the mean
• In statistics, regression toward (or to) the mean is the
phenomenon that if a variable is extreme on its first
measurement, it will tend to be closer to the average on its
second measurement—and if it is extreme on its second
measurement, it will tend to have been closer to the
average on its first.
• the practice of health care in which the practitioner
systematically finds, appraises, and uses the most
current and valid research findings as the basis for
clinical decisions. The term is sometimes used to
denote evidence-based medicine specifically but can
also include other specialties, such as evidence-
based nursing, pharmacy, and dentistry.
• The judicious use of the best current evidence in making
decisions about the care of the individual patient.
Acceptable definition of EBP?
• an approach to decision making in which the clinician uses
the best evidence available, in consultation with the patient,
to decide upon the option which suits the patient best. (Muir
Where do we find evidence?
• Evidence synthesis databases