Tip #42: PubMed Subheadings and Explosion

Many thanks to Molly K. Maloney, Pharmacy Liaison Librarian, University at Buffalo, mkm9@buffalo.edu, and Marijane White, Data and Research Engagement Librarian, Oregon Health & Science University, whimar@ohsu.edu for this week’s tip.

Molly and Marijane would like to acknowledge and thank Barbara S. Reich, Director, Medical Library, Hackensack University Medical Center, barbara.reich@hmhn.org, Paije Wilson, Health Sciences Librarian, University of Wisconsin-Madison, paije.wilson@wisc.edu, and Michelle L. Zafron, Associate Librarian, University at Buffalo, mlzafron@buffalo.edu for their contributions to this conversation.

In a recent post on the Expert Searching mailing list, Molly asked,

"In helping a student craft a search that includes a MeSH term with subheading, I realized I was assuming the subheading carry over to the child terms when exploded. As an example, if searching for "Mental Disorders/pathology"[Mesh] will you also get "Anxiety Disorders/pathology"[Mesh] in your results?"

Marijane replied:

"This is the kind of thing that I try to figure out by running and comparing searches. If you do a search for “Anxiety Disorders/pathology”[Mesh] and then do another search for (“Anxiety Disorders/pathology”[Mesh] AND “Mental Disorders/pathology”[Mesh]), you’ll find that both searches will have the same number of results. This means all the results for the narrower term are wholly contained within the results for the broader term and we can conclude that using subheadings does not turn off explosion in PubMed."

Paije Wilson also contributed that you could confirm this with a NOT search as well.

Molly’s Searches:
"Mental Disorders/pathology"[Mesh]
"Anxiety Disorders/pathology"[Mesh]

Marijane’s Test:
"mental disorders/pathology"[MeSH Terms] AND "anxiety disorders/pathology"[MeSH Terms]

Paije’s Test:
"anxiety disorders/pathology"[MeSH Terms] NOT "mental disorders/pathology"[MeSH Terms]

Molly’s colleague Michelle Zafron pointed out that this might not always be the case:

"I just tried this using a different example and it gets me different numbers. I searched on ("Breast Neoplasms/diagnosis"[Mesh]) AND ("Breast Carcinoma In Situ/diagnosis"[Mesh]) By itself the former has 66,023 and the later 3,144. When I search with AND I get 2,841."

Michelle’s Test:
"breast neoplasms/diagnosis"[MeSH Terms] AND "breast carcinoma in situ/diagnosis"[MeSH Terms]

Barbara Reich also followed up, noting that Breast Carcinoma in Situ is also a narrower term for Carcinoma in Situ, and that the difference is independent of whether subheadings are used. This encouraged Marijane to investigate further, where she noticed that it also has different narrower terms in that tree, and that it appears Carcinoma, Intraductal, Noninfiltrating is responsible for the difference in results.

Barbara’s Tests:
("Breast Neoplasms"[MeSH])
("Breast Carcinoma In Situ"[Mesh])
(("Breast Neoplasms"[MeSH])) AND (("Breast Carcinoma In Situ"[Mesh]))

Marijane’s Tests:
("Breast Carcinoma In Situ"[Mesh]) NOT ("Breast Neoplasms"[Mesh])
("Carcinoma, Intraductal, Noninfiltrating"[Mesh]) NOT ("Breast Neoplasms"[Mesh])
(("Carcinoma, Intraductal, Noninfiltrating"[Mesh]) OR ("Paget's Disease, Mammary"[Mesh])) NOT ("Breast Neoplasms"[Mesh])

In further conversation off-list, Paije suggested a test to see if a subheading will only retrieve MeSH terms lower on the hierarchy that have the same subheading utilizing NOT. In the case of a test using Dissociative Disorders and Dissociative Identity Disorder with the pathology subheading, Paije observes:

"This will be 0 results, because it's automatically applying the subheading to dissociative identity disorder, as well (i.e., you can't retrieve dissociative identity disorder unless it has that pathology subheading)."

Molly experimented with this test in a context of multiple child terms using Attention Deficit and Disruptive Behavior Disorders and Attention Deficit disorder with Hyperactivity. The four results returned did indeed include a different child term, Conduct Disorder, with the pathology subheading, demonstrating the explosion, but it also returned PMID: 18764966 which met the requirements of the search through including both Attention Deficit and Disruptive Behavior Disorders/pathology AND Attention Deficit Disorder with Hyperactivity with no subheading.

Marijane simplified the test by combining the parent term Dissociative Disorders with the pathology subheading with the child term Dissociative Identity Disorder alone. The results can then be compared with the results of a search for the child term with the subheading.
This test replicated with Molly’s search terms returns the same result as well.

Paije’s Test:
"dissociative disorders/pathology"[MeSH Terms] AND ("dissociative identity disorder"[MeSH Terms] NOT "dissociative identity disorder/pathology"[MeSH Terms])

Molly’s Test:
"attention deficit and disruptive behavior disorders/pathology"[MeSH Terms] AND ("attention deficit disorder with hyperactivity"[MeSH Terms] NOT "attention deficit disorder with hyperactivity/pathology"[MeSH Terms])

Marijane’s Test:
("dissociative disorders/pathology"[MeSH Terms]) AND ("dissociative identity disorder"[MeSH Terms])
"dissociative identity disorder/pathology"[MeSH Terms]

 

This is all to say, if you have a question about how PubMed works, try asking PubMed directly!