More about search filters

This follows on from an earlier post about the ISSG Search Filter Resource.

In Medline and some other databases, you can limit a search to a particular publication type, for example, an RCT.  But publication types are not always consistently indexed in Medline, with some references that are RCTs not indexed as such, and some which are not RCTs indexed as if they were.  

Very new references will not have any indexing, so will have no publication type.   They will therefore be missed if you rely on the publication type limit.

So, relying on publication type limits may cause you problems if you are conducting a systematic review and need to find all RCTs on your topic.

A search filter is a search strategy that finds a particular publication type.  For example, this, from SIGN, to find RCTs:

1	Randomized Controlled Trials as Topic/
2	randomized controlled trial/
3	Random Allocation/
4	Double Blind Method/
5	Single Blind Method/
6	clinical trial/
7	clinical trial, phase i.pt
8	clinical trial, phase ii.pt
9	clinical trial, phase iii.pt
10	clinical trial, phase iv.pt
11	controlled clinical trial.pt
12	randomized controlled trial.pt
13	multicenter study.pt
14	clinical trial.pt
15	exp Clinical Trials as topic/
16	or/1-15
17	(clinical adj trial$).tw
18	((singl$ or doubl$ or treb$ or tripl$) adj (blind$3 or mask$3)).tw
19	PLACEBOS/
20	placebo$.tw
21	randomly allocated.tw
22	(allocated adj2 random$).tw
23	or/17-22
24	16 or 23
25	case report.tw
26	letter/
27	historical article/
28	or/25-27
29	24 not 28

This uses MeSH headings that might be applied to an RCT, but also title or abstract words that might indicate that a study is an RCT.

The ISSG Search Filter Resource links to search filters for retrieving different study designs, and to information about designing search filters.  

If you are doing a systematic search (including, but not only, searches for evidence for systematic reviews), we recommend looking at the ISSG Search Filter Resource.    For advice on search filters, please do contact your Clinical Librarian.