Question: Why does exploding the thesaurus term “drug therapy” in Embase or Medline thesauri return less records than the searching specifically for “drug therapy” in these thesauri?

Answer: Normally, when exploding a term in either the Medline (MeSH) or Embase (Emtree) thesauri, this retrieves more records than searching specifically for that term. That is expected behaviour. However, as illustrated below:

Emb.exact(“drug therapy”)                     retrieved 4731250 records                                  
Emb.exact.explode(“drug therapy”)     retrieved 3184383 records                                  
Mesh.exact(“drug therapy”)                   retrieved 2250093 records                                  
Mesh.exact.explode(“drug therapy”)   retrieved 1418935 records                                  

When searching a thesaurus term, which also appears as a subheading (qualifier), the reverse is true. What is happening is that when you search for these terms, the platform is not only searching for that particular thesaurus term, it is also searching for the subheading, no matter to which thesaurus term it is attached to.

Examples are:

Epilepsies, Myoclonic -- drug therapy (major);
streptozotocin-induced diabetes mellitus -- drug therapy -- dichloroacetic acid (major);

To discover how many records are being retrieved as qualifiers, instead of emtree/mesh terms, use the following search command:

Qu(“drug therapy”)

QU field code that allows you to search for a term as a qualifier alone

Then search:

Emb.exact(“drug therapy”) not qu(“drug therapy”)  and this will retrieve records that only have drug therapy as an emtree term.

mesh.exact(“drug therapy”) not qu(“drug therapy”)  and this will retrieve records that only have drug therapy as a mesh term.