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What’s all this MeSH?

What’s all this MeSH?. An introduction to Medical Subject Headings www.bradfordvts.co.uk. From the guru of EBM -.

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What’s all this MeSH?

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  1. What’s all this MeSH? An introduction to Medical Subject Headings www.bradfordvts.co.uk

  2. From the guru of EBM - ‘MEDLINE is the best general source of current best evidence at present because of its breadth and constant maintenance. Thus, it is important to evidence-based practice that clinicians develop and hone MEDLINE searching skills and acquire local access.’ Evidence-based Medicine: how to practice & teach EBM - Sackett D L et al 1998

  3. Medline • Library (Ovid windows) • Hospital network (Knowledge Finder) • BMA (Ovid web) • PubMed (web) • Internet Grateful Med (web) • Other (Silver Platter, Dialog .....)

  4. Three great lies ... • The cheque is in the post • Of course I’ll still respect you in the morning • MeSH is exciting

  5. MeSH • Removes the uncertainty • Have I thought of all the synonyms? • Have I tried all the spellings? • Have I included all the variants? • Did the author use my term(s) at all?

  6. Playing the game • The indexers set the rules - you have to play by them!

  7. From broad to specific • Start off by being inclusive - keep it broad • THEN narrow it down by using limits • Narrowing too soon will make you miss things

  8. The tree structure • Respiratory tract diseases • Bronchial Diseases • Asthma • Asthma, Exercise-Induced • Status Asthmaticus • Ciliary Motility Disorders • .................... • Laryngeal Diseases • ......................

  9. No misspelt MeSH • MeSH terms are never misspelt as they are entered automatically not manually

  10. The most specific term • Intestinal neoplasms 591 • Cecal neoplasms 136 • Colonic neoplasms 4929 • Duodenal neoplasms 385 • Ileal neoplasms 227 • Intestinal polyps 260 • Jejunal neoplasms 189 • Rectal neoplasms 2189

  11. Exploding • Bronchial Diseases • Asthma • Asthma, Exercise-Induced • Status Asthmaticus

  12. Difficult asthma (a letter) *Asthma/px [Psychology] Asthma/th [Therapy] Child Human Practice Guidelines Psychology, Social

  13. Focus (& textwords) 1 *asthma 7517 2 asthma/ 9108 3 asthma.tw. 9795 4 1 not 3 1000 5 2 not 3 1780 6 3 not 2 2467

  14. Friedrich Wilhelm I and porphyria ‘The diagnosis of porphyria was not recognized then and other names were used such as ..... asthmaspasmodica flatulentum .....’

  15. Subheadings for Asthma • classification • complications • diagnosis • epidemiology • prevention & control • psychology • surgery ...........................

  16. Exploding subheadings Therapeutic use • tu.xs. • administration & dosage • adverse effects • contraindications • poisoning

  17. Diagnosis di.xs pathology radiography radionuclide imaging ultrasonography Pharmacology ph.xs. admin & dosage adverse effects contraindications diagnostic use pharmakinetics poisoning toxicity Exploding subheadings

  18. Combining 1 *self-help groups 445 2 support groups.tw. 257 3 *asthma 7708 4 1 or 2 615 5 3 and 4 6 6 self-help groups/ 798 7 6 and 3 6 8 7 not 5 2

  19. OR is MORE

  20. Limits • Local holdings (for library only) • Age groups • Publication types • Language • Year of publication • Human/animal • etc

  21. Still too much? • Use the most specific subject headings • Use focus • Use subheadings • Use AND • Use limits • Restrict textword searching to title

  22. Or too little? • Use OR • Use explode • Use All Subheadings • Don’t use focus • Consider synonyms, alternative spellings or truncation

  23. And always remember • Check the MeSH headings used for the most relevant articles and add them to your search if necessary. • You cannot find what is not there!

  24. Sensitivity and Specificity • If a search is too sensitive, it will retrieve too much irrelevant material • If a search is too specific, it will miss relevant material

  25. WHY are you searching? • Do you want one decent article on a topic? • Do you need evidence? • Are you writing a letter/book/article/systematic review?

  26. WHAT are you looking for? • Systematic reviews • Clinical trials • Traditional reviews • Guidelines • General information • Letters

  27. Look in the right place • Full-text systematic reviews - on CL • All Medline clinical trials + others are in Cochrane Controlled Trials Register • Cochrane looks only at EFFECTIVENESS • Medline includes a very wide range of publications & can answer a wide range of questions

  28. Cochrane Library for effectiveness questions - diagnosis, prognosis, treatment Medline for other questions - general information, epidemiology, aetiology, surgical techniques etc The right place to look

  29. MeSH on Cochrane Library • Many items on the CL are indexed with MeSH terms • BUT not all of them are • SO the offical recommendation is to use MeSH and textword searching combined

  30. Text word searching • Looks for exact matches • Doesn’t allow for • variants - pregnancy, pregnant, pregnancies • alternative spellings - diarrhoea, diarrhea • synonyms - preterm birth, premature birth; cancer, neoplasm Apart from Knowledge Finder which uses fuzzy logic

  31. Fields The different parts of each item on a database are called fields, and most can be searched individually. In Ovid • ti = title • au = author • ab = abstract • tw = textword (title or abstract) • in = institution • pg = page

  32. What you miss • oral thrush 27 • candidiasis, oral/ 412 • breast cancer 13879 • breast neoplasms/ 18754

  33. What you miss?? • heart attack 236 • myocardial infarction 11040 • myocardial infarction/ 10091 = 949 irrelevant articles - at least!!

  34. Stop words • Many common, normally insignificant, words are ignored in free text searching. This can be a problem when looking for concepts such as ‘out-of-hours’ or ‘after-hours’. There is no way round this unless there is a relevant subheading. In this case there isn’t!!

  35. Hyphens • Different systems treat these in different ways. They may be ignored or treated as spaces or treated as hyphens. • To be safe try all options eg • postnatal • post natal • post-natal

  36. Mizspellins • Ray & Vermeulen found a total of 200 instances of 10 misspelt textwords in Medline between 1966 and 1996. Ray J G & Vermeulen M J BMJ 1996 313:1658-9

  37. 1996-1999 • antibotics 4 • asprin 1 • dopler 2 • cholestrol 1 • thrombolism 3 • myocardial infraction 34

  38. haemorrhage?? • hamorrhage 1 • haemorhage 3 • hemorhage 1 and no doubt there’s more!!

  39. Truncation This can be used to overcome some of the problems of free text searching. Different wild cards are used by different systems. Mainly * $ and ? Can be used at the end of a word for truncation eg pregnan$ or in the middle for spelling variants eg wom?n, an?emia

  40. Textword advantages • New concepts eg new drugs • British concepts eg clinical governance, Project 2000 • Tradenames MeSH headings are updated annually

  41. Further reading • Sackett D L et al - Evidence-based medicine: how to practice & teach EBM. Churchill Livingstone, 1998 • Roberts R - Information for evidence-based care. Radcliffe, 1999 • Chambers R - Clinical effectiveness made easy. Radcliffe, 1998

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