The first step in finding the evidence is to ask the right question!
There is an art to constructing a clinical question in such a way that you maximise your chances of finding meaningful information in an efficient manner.
For example, imagine the following scenario:
Your patient is a thirty year old woman, 14 weeks pregnant with her first child. On an initial antenatal visit she is found to have a BMI of 32, putting her in the obese range. You are concerned about the risk of adverse outcomes for the woman and her baby, especially if she gains a lot of weight during her pregnancy. You wonder whether dietary or lifestyle interventions could help your patient limit her weight gain during the remainder of her pregnancy.
One approach to turn our scenario into a clinical question is to use the PICOT formula. This helps us to pick out the key point from our scenario.
P = Patient or Population or Problem
"thirty year old woman, 14 weeks pregnant with her first child.....BMI of 32"
I = Intervention
"dietary or lifestyle interventions"
C = Comparison
O = Outcome
"limit her weight gain during pregnancy"
T = Type of study
Question = therapy; study type = RCT or systematic review
The next step is to translate the key points we have identified into keywords.
When considering keywords, it is important to choose terms which will help us find the information we need, without narrowing down our search too much. For example "BMI of 32" is too specific; "obese" would be a better term.
We also need to consider synonyms, or alternative terms, for our keywords, in order to capture as many relevant articles as possible. For example, alternative terms for "lifestyle intervention" could include "exercise" or "diet".
Next we need to consider dropping some terms which may be redundant. For example, if we include the term "pregnant" or "antenatal" we don't need the term "woman". If the comparison is "usual care", we don't need to specify this in our keywords.
Finally, we need to think how to form our terms into an effective search strategy. We combine alternative terms with OR and terms for different concepts with AND.
We could end up with something like this:
obese OR overweight
pregnant OR pregnancy OR antenatal OR prenatal
lifestyle OR diet OR exercise
weight gain OR excessive weight
limit to Systematic Reviews or RCTs.
The table below explains how Boolean Operators (AND, OR, NOT) work