"Subtracting" Results
Would you like to see the difference between two search strings? Using the NOT function in Advanced Search allows you to do that.
For example, let's say you are looking for results pertaining to shoulder injuries in children. You have a search string that pertains directly to the shoulder, but you also have one that includes more general terms such as "upper arm." You'd like to see the difference between the two; that is to say, you'd like to see the extra citations that the broader search returns, but are missed by the more narrow search.
- 3,000+ results: (Shoulder OR acromion OR glenohumeral OR scapula* OR scapulothoracic ) AND (injury) AND (children OR pediatric)
- 5,000+ results: (Shoulder OR acromion OR glenohumeral OR scapula* OR scapulothoracic OR "upper arm" OR "upper extremity" OR "upper limb") AND (injury) AND (children OR pediatric)
Steps
First, run the separate searches in PubMed. Next, go into Advanced Search (the link is right below the search box).
Click the three dots (under Actions) in front of the search string that returns the larger set of results, and choose "Add Query." This adds it to the Search Query Builder box above.
Next click the three dots (under Actions) in front of the search string that returns the smaller set of results, and choose "Add with NOT. " This also adds this to the Search Query Builder box above.
Hit the blue Search button, and you should get the 2000 results that appear in one search but not the other.
It is as if you just did a subtraction math problem: 5000 - 3000 and now you should see the 2000 difference.
Note: When you are reviewing results, remember that PubMed returns results based on a "Best Match" algorithm. It might make sense to change this to "Most Recent." This allows for a more realistic idea of your results, not just those that match your search criteria especially well. You can make this change by clicking the Display Option box on the PubMed results page.
