Developing and validating a palliative care subject search filter

Background
Efficient access to relevant information underpins efforts to translate research evidence into practice. Palliative care clinicians and researchers face many informational challenges including the diverse areas in which palliative care information may be published and a lack of descriptiveness and consistent terminology to support searching.

Objective
To formulate and evaluate palliative care search filters for use in the general medical literature.

Methods
Four general medical journals (BMJ, Lancet, Annals of Internal Medicine, and JAMA from 1999 to 2001) were handsearched by palliative clinicians and researchers to identify articles and items relevant to palliative care, forming a ”gold standard” reference set (GS). A series of search strategies comprising MeSH terms and textwords were created for use in Ovid Medline (OM) by an expert librarian and palliative clinicians and researchers.

Retrieved references from the OM searches were compared to the GS references using a specially written computer program that automatically calculated the sensitivity, specificity, accuracy and precision of the OM searches.

Results and conclusions
773/20501 (3.8%) relevant articles were identified by hand-searching. A master search combining nine MeSH descriptors with three textwords achieved 45.4% sensitivity, 99.3% specificity, 73% precision and 97.3% accuracy. Efforts to increase the sensitivity by modifying three relevant published but unvalidated searches did not improve the yield, except in one case which resulted in an improved sensitivity of 56.9%, but offset by reduced specificity (92.1%), precision (22%) and accuracy (90.8%). We confirmed that palliative care literature is difficult to identify in the general literature. Whilst our filter represents the best trade-off between sensitivity, specificity, accuracy and precision, the sensitivity is unacceptably low. Further research, such as frequency analysis of textwords and MeSH terms, is required to increase the sensitivity of searching.