Developing a search that informs a systematic review is an iterative process.
Carry out the search as outlined in Step 7, entering each term from the Concept Table into the database and using the search history to combine the terms with AND and OR appropriately. You can easily spot mistakes by looking at the number of search results for each term. You can also identify which terms add value to the search. Keep an eye out for searches returning 0 results (they are not adding "value" or have a mistake) and searches returning a very high number of results (term may be too broad). If you decide to remove a term, make a note of why.
It is important to constantly look at the search results to determine whether the results are relevant. Ask yourself whether already identified key articles are being found by the search. If not, review these known articles for words in the title and abstract, author's keywords and, if available, controlled vocabulary terms. Revise your search strategy by adding any missing terms and re-run the search if necessary.
For more information on documenting your search, see the Documenting Search Strategies tab.
After running your pilot search it is important that you evaluate the search results before translating the search for the other databases or commencing the screening process. You can do this by asking yourself these questions:
NOTE! Developing your search is an iterative process. You usually have to modify your original search several times.
Did I find too many results?
There is no "good" or "right" number of search results. The number of search results will depend on how much research has been done on your topic.
If you find thousands of results, check whether the results are mainly relevant (see Relevant results?). If they are, you may like to make your question more specific and add an extra concept.
Did I find too few results?
There is no "good" or "right" number of search results. The number of search results will depend on how much research has been done on your topic.
You may like to ask yourself these questions:
Are the results I found relevant?
Every search will find some irrelevant results, it's inevitable. However if you find far too many irrelevant results, consider the following:
Do the search results contain the known key articles?
A good search should pick up the known key articles on your topic.
If not, check the the following:
The aim of the PRESS 2015 Guideline Statement is to help guide and improve the peer review of electronic literature search strategies.
You may like to use the PRESS checklist to self-critique your search strategies.
This video from the The Medical Library at Yale University introduces techniques in validating, verifying and revising your searches:
The University of Newcastle has developed a checklist for reviewing search strategies:
This is the search history for our example search in Medline via Ovid (result numbers for search done on 16 October 2020), following Step 7. Each term is searched for separately and the individual searches are then combined with OR and AND using the Search History.
|
# |
Searches |
Results |
| 1 | Dementia.ab,kf,ti. | 119329 |
| 2 | Alzheimer.ab,kf,ti. | 30558 |
| 3 | "Huntington*".ab,kf,ti. | 19155 |
| 4 | Kluver.ab,kf,ti. | 552 |
| 5 | Lewy.ab,kf,ti. | 10352 |
| 6 | exp Dementia/ | 167832 |
| 7 | 1 or 2 or 3 or 4 or 5 or 6 | 236562 |
| 8 | (Animal adj3 therap*3).ab,kf,ti. | 1773 |
| 9 | (Animal adj3 activit*).ab,kf,ti. | 3639 |
| 10 | (Animal adj3 intervention*).ab,kf,ti. | 892 |
| 11 | (Pet adj3 therap*3).ab,kf,ti. | 1324 |
| 12 | (Dog adj3 therap*3).ab,kf,ti. | 331 |
| 13 | (Canine adj3 therap*3).ab,kf,ti. | 499 |
| 14 | Aquarium.ab,kf,ti. | 2023 |
| 15 | Animal Assisted Therapy/ | 430 |
| 16 | Pets/ | 2583 |
| 17 | Dogs/ | 327033 |
| 18 | Cats/ | 135457 |
| 19 | Birds/ | 38348 |
| 20 | Bonding, Human-Pet/ | 1883 |
| 21 | Animals, Domestic/ | 15577 |
| 22 | 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19 or 20 or 21 | 499538 |
| 23 | "music*".ab,kf,ti. | 23820 |
| 24 | singing.ab,kf,ti. | 3489 |
| 25 | sing.ab,kf,ti. | 1366 |
| 26 | "Auditory stimulat*".ab,kf,ti. | 1987 |
| 27 | Music/ | 14161 |
| 28 | Music Therapy/ | 3582 |
| 29 | Acoustic Stimulation/ | 43715 |
| 30 | Singing/ | 897 |
| 31 | 23 or 24 or 25 or 26 or 27 or 28 or 29 or 30 | 73975 |
| 32 | Aggression.ab,kf,ti. | 31826 |
| 33 | Neuropsychiatric.ab,kf,ti. | 34382 |
| 34 | Apathy inventory.ab,kf,ti. | 37 |
| 35 | Cornell scale.ab,kf,ti. | 392 |
| 36 | Cohen Mansfield.ab,kf,ti. | 360 |
| 37 | BEHAVE-AD.ab,kf,ti. | 166 |
| 38 | CERAD-BRSD.ab,kf,ti. | 5 |
| 39 | behavio?r.ab,kf,ti. | 922413 |
| 40 | exp Aggression/ | 38628 |
| 41 | exp Personality Inventory/ | 36368 |
| 42 | Psychomotor Agitation/ | 5189 |
| 43 | 32 or 33 or 34 or 35 or 36 or 37 or 38 or 39 or 40 or 41 or 42 | 1019967 |
| 44 | 7 and 22 and 31 and 43 | 7 |
All of the search terms that were identified in Step 3 and Step 4, return some results and add value. The final search combining all four concepts only returned seven results. It's easier to scan these articles for a RCT study design than to add the methodological search filter for RCTs as another concept. Also, it's best to use the fewest concepts possible in a search when conducting a systematic review.
This is the search history for our example search in Medline via PubMed (result numbers for search done on 19 May 2017), following Step 7. Each term is searched for separately and the individual searches are then combined with OR and AND using the History and Query box.
Note! PubMed's search history displays the searches in reverse chronological order (latest search on top).
|
Search |
Query |
Results |
| #48 | #7 AND #24 AND #34 AND #47 | 10 |
| #47 | #35 OR #36 OR #37 OR #38 OR #39 OR #40 OR #41 OR #42 OR #43 OR #44 OR #45 OR #46 | 1,469,606 |
| #46 | Psychomotor agitation [mh] | 6,642 |
| #45 | Personality inventory [mh] | 36,769 |
| #44 | Aggression [mh] | 40,623 |
| #43 | Behaviour* [tiab] | 309,598 |
| #42 | Behavior* [tiab] | 1,084,895 |
| #41 | CERAD-BRSD [tiab] | 5 |
| #40 | BEHAVE-AD [tiab] | 166 |
| #39 | Cohen Mansfield [tiab] | 372 |
| #38 | Cornell scale [tiab] | 396 |
| #37 | Apathy inventory [tiab] | 34 |
| #36 | Neuropsychiatric [tiab] | 35,245 |
| #35 | Aggression [tiab] | 32,027 |
| #34 | #25 OR #26 OR #27 OR #28 OR #29 OR #30 OR #31 OR #32 OR #33 | 74,990 |
| #33 | Singing [mh] | 1,050 |
| #32 | Acoustic Stimulation [mh] | 44,925 |
| #31 | Music Therapy [mh] | 3,867 |
| #30 | Music [mh] | 15,005 |
| #29 | Auditory stimulat* [tiab] | 1,956 |
| #28 | Sing [tiab] | 1,400 |
| #27 | Singing [tiab] | 3,552 |
| #26 | Music* [tiab] | 23,586 |
| #25 | Music therapy [tiab] | 2,692 |
| #24 | #8 OR #9 OR #10 OR #11 OR #12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR #22 OR #23 | 501,702 |
| #23 | Animals, Domestic [mh:noexp] | 15,819 |
| #22 | Bonding, Human-Pet [mh] | 1,955 |
| #21 | Birds [mh:noexp] | 39,601 |
| #20 | Cats [mh] | 137,266 |
| #19 | Dogs [mh] | 332,958 |
| #18 | Pets [mh] | 2,922 |
| #17 | Animal Assisted Therapy [mh:noexp] | 489 |
| #16 | Aquarium [tiab] | 2,029 |
| #15 | Canine-assisted therapy [tiab] | 20 |
| #14 | Dog-assisted therapy [tiab] | 33 |
| #13 | Dog therapy [tiab] | 14 |
| #12 | Pet therapy [tiab] | 164 |
| #11 | Animal therapy [tiab] | 70 |
| #10 | Animal-assisted intervention* [tiab] | 215 |
| #9 | Animal-assisted activit* [tiab] | 81 |
| #8 | Animal-assisted therapy [tiab] | 368 |
| #7 | #1 OR #2 OR #3 OR #4 OR #5 OR #6 | 287,217 |
| #6 | Dementia [mh] | 179,610 |
| #5 | Lewy [tiab] | 10,599 |
| #4 | Kluver [tiab] | 552 |
| #3 | Huntington* [tiab] | 19,152 |
| #2 | Alzheimer [tiab] | 162,646 |
| #1 | Dementia [tiab] | 121,679 |
All of the search terms that were identified in Step 3 and Step 4, return some results and add value. The final search combining all four concepts only returned seven results. It's easier to scan these articles for a RCT study design than to add the methodological search filter for RCTs as another concept. Also, it's best to use the fewest concepts possible in a search when conducting a systematic review.
