Subheadings are used to further describe a particular aspect of a subject heading in databases such as Medline, Embase and Cinahl.
An example might be (for Medline) 'thromboembolism/prevention and control' or the two-letter subheading abbreviation -- thromboembolism/pc. 'Thromboembolism' is the subject heading and 'prevention and control' one of its subheadings (this will retrieve a subset of the results which have been tagged with the thromboembolism subject heading, limiting the results to only those articles discussing the prevention and control aspect).
However, it is possible in these databases to search for the subheading independent of any subject heading. This allows you to retrieve all articles which have been tagged with a particular subheading but without having to specify what subject headings it is attached to. A list of subheadings and abbreviations is available.
This can be very useful as seen in the example below where the search aims to retrieve any article in Medline tagged with the floating subheadings of Adverse Effects (ae), Complications (co) or Drug Effects (de) [search line 43] . In the Ovid databases to search using floating subheadings you can type the two letter subheading abbreviation followed by .fs. Keyword searches for safety, side effects, toxicity, adverse effects, etc were also undertaken in the search strategy [search lines 44-45] and the results brought together using OR [search line 46] before being combined with other elements of the search, e.g. the specific patient population and drug intervention which was being reviewed [for the full search strategy see the Appendix of the Cochrane Review linked below].
43. (ae or co or de).fs.
44. (safe or safety or (side adj1 effect*) or (undesirable adj1 effect*) or (treatment adj1 emergent) or tolerability or tolerance or tolerate or toxicity or toxic or adrs or adr or harm or harms or harmful or complication* or risk or risks or (unintended adj1 event*) or (unintended adj1 effect*)).ti,ab.
45. (adverse adj2 (effect or effects or reaction or reactions or event or events or outcome or outcomes)).ti,ab.
46. 43 or 44 or 45
Extract of Medline (Ovid) search strategy from: Storebø, O., Ramstad, E., Krogh, H., Nilausen, T., Skoog, M., Holmskov, M., Rosendal, S., Groth, C., Magnusson, F.L., Moreira-Maia, C.R., Gillies, D., Buch Rasmussen, K., Gauci, D., Zwi, M., Kirubakaran, R., Forsbøl, B., Simonsen, E., Gluud, C. (2015), 'Methylphenidate for children and adolescents with attention deficit hyperactivity disorder (ADHD)', Cochrane Database of Systematic Reviews, Issue 11. Art. No.: CD009885. DOI: 10.1002/14651858.CD009885.pub2