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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

What’s all this MeSH?

An introduction to

Medical Subject Headings

www.bradfordvts.co.uk

from the guru of ebm
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

medline
Medline
  • Library (Ovid windows)
  • Hospital network (Knowledge Finder)
  • BMA (Ovid web)
  • PubMed (web)
  • Internet Grateful Med (web)
  • Other (Silver Platter, Dialog .....)
three great lies
Three great lies ...
  • The cheque is in the post
  • Of course I’ll still respect you in the morning
  • MeSH is exciting
slide5
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?
playing the game
Playing the game
  • The indexers set the rules - you have to play by them!
from broad to specific
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
the tree structure
The tree structure
  • Respiratory tract diseases
    • Bronchial Diseases
      • Asthma
        • Asthma, Exercise-Induced
        • Status Asthmaticus
    • Ciliary Motility Disorders
      • ....................
    • Laryngeal Diseases
      • ......................
no misspelt mesh
No misspelt MeSH
  • MeSH terms are never misspelt as they are entered automatically not manually
the most specific term
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
exploding
Exploding
  • Bronchial Diseases
    • Asthma
      • Asthma, Exercise-Induced
      • Status Asthmaticus
difficult asthma a letter
Difficult asthma (a letter)

*Asthma/px [Psychology]

Asthma/th [Therapy]

Child

Human

Practice Guidelines

Psychology, Social

focus textwords
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

friedrich wilhelm i and porphyria
Friedrich Wilhelm I and porphyria

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

subheadings for asthma
Subheadings for Asthma
  • classification
  • complications
  • diagnosis
  • epidemiology
  • prevention & control
  • psychology
  • surgery ...........................
exploding subheadings
Exploding subheadings

Therapeutic use

  • tu.xs.
    • administration & dosage
    • adverse effects
    • contraindications
    • poisoning
exploding subheadings17
Diagnosis

di.xs

pathology

radiography

radionuclide imaging

ultrasonography

Pharmacology

ph.xs.

admin & dosage

adverse effects

contraindications

diagnostic use

pharmakinetics

poisoning

toxicity

Exploding subheadings
combining
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

limits
Limits
  • Local holdings (for library only)
  • Age groups
  • Publication types
  • Language
  • Year of publication
  • Human/animal
  • etc
still too much
Still too much?
  • Use the most specific subject headings
  • Use focus
  • Use subheadings
  • Use AND
  • Use limits
  • Restrict textword searching to title
or too little
Or too little?
  • Use OR
  • Use explode
  • Use All Subheadings
  • Don’t use focus
  • Consider synonyms, alternative spellings or truncation
and always remember
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!
sensitivity and specificity
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
why are you searching
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?
what are you looking for
WHAT are you looking for?
  • Systematic reviews
  • Clinical trials
  • Traditional reviews
  • Guidelines
  • General information
  • Letters
look in the right place
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
the right place to look
Cochrane Library for effectiveness questions - diagnosis, prognosis, treatment

Medline for other questions - general information, epidemiology, aetiology, surgical techniques etc

The right place to look
mesh on cochrane library
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
text word searching
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

fields
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
what you miss
What you miss
  • oral thrush 27
  • candidiasis, oral/ 412
  • breast cancer 13879
  • breast neoplasms/ 18754
what you miss33
What you miss??
  • heart attack 236
  • myocardial infarction 11040
  • myocardial infarction/ 10091

= 949 irrelevant articles - at least!!

stop words
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!!
hyphens
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
mizspellins
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

1996 1999
1996-1999
  • antibotics 4
  • asprin 1
  • dopler 2
  • cholestrol 1
  • thrombolism 3
  • myocardial infraction 34
haemorrhage
haemorrhage??
  • hamorrhage 1
  • haemorhage 3
  • hemorhage 1

and no doubt there’s more!!

truncation
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

textword advantages
Textword advantages
  • New concepts eg new drugs
  • British concepts eg clinical governance, Project 2000
  • Tradenames

MeSH headings are updated annually

further reading
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