a descriptor will include all the descriptors in the hierarchy below the given one. PubMed does not apply automatic mapping of the term in the following circumstances: by writing the quoted phrase (e.g., "kidney allograft"), when truncated on the asterisk (e.g., ), and when looking with field labels (e.g., ). Use at ClinicalTrials.gov At ClinicalTrials.gov, each trial has keywords that describe the trial. The ClinicalTrials.gov team assigns each trial two sets of MeSH terms. One set is for the conditions studied by the trial and the other for the set of interventions used in the trial. The XML file that can be downloaded for each trial contains these MeSH keywords. The XML file also has a comment that says: "the assignment of MeSH keywords is done by imperfect algorithm". Categories The top-level categories in the MeSH descriptor hierarchy are: Anatomy [A] Organisms [B] Diseases [C] Chemicals and Drugs [D] Analytical, Diagnostic and Therapeutic Techniques, and Equipment [E] Psychiatry and Psychology [F] Phenomena and Processes [G] Disciplines and Occupations [H] Anthropology, Education, Sociology and Social Phenomena [I] Technology, Industry, and Agriculture [J] Humanities [K] Information Science [L] Named Groups [M] Health Care [N] Publication Characteristics [V] Geographicals [Z] See also Medical classification Medical literature retrieval References External links Medical Subject Heading Home provided by National Library of Medicine, National Institutes of Health (U.S.) MeSH database tutorials Automatic Term Mapping Browsing MeSH: Entrez MeSH Browser Visual MeSH Browser mapping drug-disease relationships in research Reference.MD List of qualifiers – 2009 Biological databases Library cataloging and classification Medical classification Thesauri United States National Library of Medicine