Systematic Literature Retrieval in PubMed

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The presentation for my PhD course on systematic literature retrieval

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  • Great article. Thanks for the info, very helpful. BTW, if anyone needs to fill out a “2004 MI MC 48, [6/04]”, I found a blank form here: "www.courts.michigan.gov" and also here "statement garnishment"
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Systematic Literature Retrieval in PubMed

  1. 1. WorkshopSystematic LiteratureRetrieval in PubMed Tuesday 11 December 2012 Wichor Bramer | Gerdien de Jonge Information specialists Medical Library (Cf-232) info.mb@erasmusmc.nl | www.erasmusmc.nl/medbib phone: 010-70 43785@wichor | slideshare.net/wichor | nl.linkedin.com/in/wichor
  2. 2. Today’s scopeWhat will you be learning today?How to search systematically Finding the right keywords Optimizing your search in PubMed to be sure you didn’t miss important articlesHow to avoid the frequent (but unknown to many) pitfallsWhat will you not be learning today?The basics of PubMed We assume you already know how to use it, you’re all experienced searchers, but we want to change the way you search.Today’s rules:- Feel free to ask any question that comes up- If you see text in red you are asked to participate in the demonstration- In your handouts important lessons are marked in a gray box Medische Bibliotheek Erasmus MC 2
  3. 3. WarningDon´t think you know what you´re about to see You al are experienced users, but have adapted methods that are counter effective.Pay close attention We teach you subtle changes in the way you search PubMed that will have great impact on your search results.And change PubMed into a more valuable tool We want to change the way you use PubMed to make it more effective!Medische Bibliotheek Erasmus MC 3
  4. 4. What databases do we use? PubMed (Medline) SLR in PubMed (today) Embase SLR in other databases (next week) Medline (OvidSP) Cochrane Central Systematic Literature Retrieval Scopus or Web-of-Science uses at least these databases PsycInfo Cinahl PEDro (etc etc) Not one of them is the absolute best, to capture all articles you need to search multiple databases (and even more)Medische Bibliotheek Erasmus MC 4
  5. 5. Discussion:Do we really need all these databases, couldn’t publishers just put their data in one spot?What is the added value of that many databases?Medische Bibliotheek Erasmus MC 5
  6. 6. Practicum (discussion): Base level (homework)1. How did the process go?2. Was it hard to find relevant articles?3. Was it hard to find a small set of articles that still contain enough relevant articles?Medische Bibliotheek Erasmus MC 6
  7. 7. Homework : results & feedbackNot using truncation ALL (5)Using automatic term mapping (let pubmed do the thinking) 4No or incorrect use of parentheses 4Using automatic query builder 2No or incorrect use of Boolean operators (AND, OR, NOT) 1Using MeSH terms only 1Using standard PubMed filters (RCT, humans) -Building a search from record numbers -Using time limits -We’d like to teach you better ways to get to better results Systematic Literature Retrieval Medische Bibliotheek Erasmus MC 7
  8. 8. Homework : best practice Myrthe Tielemans ("Pregnancy"[Mesh] OR pregnancy OR preconceptional) AND ("Depression, Postpartum"[Mesh] OR "postpartum depression" OR depression OR "postnatal depression") AND (dietary patterns OR diet OR nutrition OR micronutrients OR macronutrients OR omega-3 OR folate OR thiamine OR "vitamine B-12" OR "polyunsaturated fatty acids" OR zinc OR iron) Pay special attention. For people with the most knowledge about PubMed it is harder to change the way you’ve always searched!Medische Bibliotheek Erasmus MC 8
  9. 9. Homework : effect of optimization You Me Only I found Only you Relevant found Eva M 524 42 36 (86%) 518 (99%) 0/1 Eva B 363 952 912 (96%) 322 (89%) Geriolda 2431 Karen / 1709 296 257 (87%) 1670 (98%) 0/2 Yannan Mateus 1413 2930 1658 (57%) 141 (10%) 6/6 Myrte 535 344 269 (78%) 460 (86%) 14/21 Rianne 4019Medische Bibliotheek Erasmus MC 9
  10. 10. Homework : problems addressed Where do you start? How do you translate your question into the right search words What do you do when no proper MeSH terms are found for (parts of) your search How can you reduce the number of hits without losing important articles How can you improve the relevance of your results Using AND, OR and parentheses Systematic Literature RetrievalMedische Bibliotheek Erasmus MC 10
  11. 11. What is Systematic Literature Retrieval ? To tell databases exactly the conditions an article has to meet to be found Without reservation or bias Long proces of optimisation and evaluation Combining results from multiple databasesWhy? Verifiable and accountable Repeatable to others, but also to yourself at a later moment. To prevent missing important articlesMedische Bibliotheek Erasmus MC 11
  12. 12. What is Systematic Literature Retrieval ? Sensitive search Specific search Goal Finding as much relevant Most of the found articles as posible articles are relevant # of hits High Much lower # of relevant Low Much higher articles missedThink about this: What do you think you would be likely to focus on in a database that lacks relevance ranking (like PubMed). And to what consequences?Medische Bibliotheek Erasmus MC
  13. 13. How to search systematically?1. What is your research question?Medische Bibliotheek Erasmus MC 13
  14. 14. What is your research question?PICO(ST)Patient / Intervention / Comparison / Outcome (Setting / Timing) can be useful, but don’t focus too much on thisDomainTherapy & Prevention / Diagnosis / Etiology & Risk / PrognosisBackground questionDiseases etc in general (handbooks, narrative reviews, etc)Foreground questionSpecific and relevant for a specific concrete problem  Systematic Literature RetrievalMedische Bibliotheek Erasmus MC
  15. 15. How to search systematically?1. What is your research question?2. What elements (key concepts) does the question contain? - are they specific or general and important or less important?Medische Bibliotheek Erasmus MC 15
  16. 16. Elements in your research question Why use elements? To determine where to start your search! Elements are distinguishable concepts in your research question:  Substances  Actions  Diseases/ symptoms  Persons  Features/ characterizations  Locations/ settings  Domains Keep in mind: Elements cannot always be translated to search terms one on one: • Sometimes a search term combines two elements • Sometimes an element has to be searched with a combination of two (or more) search terms • Broccoli Cancer Prevention Very frequently an element can be found in multiple mesh terms What are not elements?  General terms, describing relations: effect, relation, significant etc etc.Medische Bibliotheek Erasmus MC
  17. 17. Elements : be careful! Bias in your elements Including outcomes in your query means bias! Including very specific characteristics mean bias! WHY? Articles that find a relevant result for a certain outcome or specific characteristic will mention that in the abstract. Accidental duplication in your elements Sometimes an element overlaps almost completely with another  Choose only the most specific Pre-ecclampsia AND pregnant AND women Broccoli Cancer meconium AND neonates Prevention But sometimes less evident: a certain therapy only used in a specific disease: Lichtenstein therapy AND inguinal herniasMedische Bibliotheek Erasmus MC
  18. 18. Elements : on a gliding scale specific generalimportant broccoli cancer prevention broccoli cancer preventionunimportantMedische Bibliotheek Erasmus MC
  19. 19. Practicum: elements4. Open a word document and describe your research question in one phrase5. Split your research question into elements, and plot them on the scale a. Are the elements very specific or more general? Are you the first using this element or do you think many more people could have used it before? Will the element result in a small set of results, or will the number be very high? b. Are they important to your question or less? Could you think of relevant articles without this element? Are elements related to each other? If there’s much overlap the most specific is the most important Medische Bibliotheek Erasmus MC 19
  20. 20. Rianne : Relationship between falls and functional status in hospitalizedadults specific generalimportant falls Functional status hospitalization adultsunimportantMedische Bibliotheek Erasmus MC
  21. 21. Eva v B : The burden of informal care of (hospitalized) elderly specific generalimportant burden elderly Informal care hospitalizationunimportantMedische Bibliotheek Erasmus MC
  22. 22. Karen / Yannan : methodologies used in studies evaluating the effect of apopulation-level policy of intervention on health inequalities specific generalimportant Population- Health level policy inequalities Evaluation studies Intervention MethodologiesunimportantMedische Bibliotheek Erasmus MC
  23. 23. How to search systematically?1. What is your research question?2. What elements (key concepts) does the question contain?3. Translate these elements (synonyms, alternatives, abbreviations) - Determine the elements to start with - List these elements in a Word file (one element per line) - Translate each element in as much relevant synonyms as possible Medische Bibliotheek Erasmus MC 23
  24. 24. Elements : where to startStart with the Important specific elementsIf a combination all important specific elements already results in a relativelysmall selection of relevant articles, stop thereAdd important general elementsIf the important specific elements generate too much hits, add extra filters forthe general elementsAdd less important elementsIf after adding all important elements still too much results appear, only thenadd the less important elements.But beware: translate them thoroughly, and allways check if the articles you Broccoli Cancerdropped by adding it can indeed be missed. Prevention If you add the less important elements you lose systematicityMedische Bibliotheek Erasmus MC
  25. 25. How do you find the right search words? Use google or wikipedia to find alternative descriptions of your topic If you dont have a clue: try typing in something and see what PubMed comes up with in search details (and use those word in you queries) Search the MeSH database  Pay attention to entry terms (but don’t use them all without reviewing), hierarchical tree, description etc..  Read the description to see if this fits your research question  Truncate every word when searching the MeSH database! Think of spelling differences (UK/USA)  Tumor / tumour; Organisation / organization; non cardiac or noncardiac; pediatrics/ paediatrics  Inversions: Quality of life / Life quality Abbreviations  Pay attention to abbreviations with multiple meanings. Then combine abbreviation with words from the complete form (clock AND draw AND test) OR (CDT AND (clock OR draw OR test))  Partially abbreviations: "sentinel LN"Medische Bibliotheek Erasmus MC
  26. 26. How do you find the right search words? Unfamiliar with English terms? Search for articles in you native languague using [tt] and scan the translated title No usefull MeSH terms available?  search for some very relevant articles and see what MeSH terms they use. Or use related articles for that. Think of the opposite. Sometimes that can be a MeSH termBut, the most important source is: Scan resulting articles for relevant terms you havent yet included in you search strategy (optimization)Medische Bibliotheek Erasmus MC
  27. 27. How to find useful filters?In the database itselfPubMed has some good standard filters (and some bad ones too) Preferred standard filters to use Rather do not use Subsets (aids, bioethics, cancer) Limits in the left side of the PubMed Sensitive Clinical Queries (therapy, result screen (humans, children, RCTs) diagnosis, etiology etc) Specific clinical queriesIn other (good) systematic reviewsOther (possibly cochrane) reviews have used the same element before. Check the appendices of that for the strategy they usedBut never take that search strategy for granted: always check if they didn’t make mistakes Translating that filter to other interfaces can be difficultMedische Bibliotheek Erasmus MC
  28. 28. Practicum : synonyms --- continue with the elements provided by the workshop leader --- --- Start to search for synonyms in the MeSH database, do not search for articles yet ---6. Translate each of these elements into synonyms a. Start with the important unique elements b. What words/ phrases are used in the controlled vocabulary (MeSH) and what type are they? Do you spot: MeSH terms, subheadings, pharmacological actions, supplementary concepts (explained later)? c. What other words can you find (synonyms / narrower terms) d. For many general elements filters exist that you can find in the database as a subset or standard seach query (for instance cancer subset or diagnosis clinical query) or evaluated and published filters (Cochrane filter for children). Medische Bibliotheek Erasmus MC 28
  29. 29. Practicum : feedbackGeriolda and Mateus:Cardiovascular diseases / riskCardiovascular Diseases[mh]CardiovascularCardiacHeart[mh]VascularBlood Vessels[mh] Medische Bibliotheek Erasmus MC 29
  30. 30. How to search systematically?1. What is your research question?2. What elements (key concepts) does the question contain?3. Translate these elements (synonyms, alternatives, abbreviations)4. Combine accoring to set theory (Boolean logic) - combine terms within an element with OR - combine elements with AND - use parentheses for priority - use truncation to search different word (or phrase) endings Medische Bibliotheek Erasmus MC 30
  31. 31. Boolean operators broccoli broccoli #2 OR AND NOT brassica cancer #1 ALWAYS USE CAPITALS FOR BOOLEAN OPERATORSpriority with parentheses: (broccoli OR brassica) AND (cancer OR neoplasm) Be careful: Automatic parentheses from query builder will result in errors ((((broccoli) OR brassica) AND cancer) OR neoplasm) Medische Bibliotheek Erasmus MC 31
  32. 32. TruncationWord truncationprevent* = prevent OR prevention OR preventing OR …etclimitations: maximum of 600 variations (mind the warning)Solution: elongate the word stem (maybe use multiple variants)Phrase truncationWhen an asterisk is used PubMed tries to do phrase truncationExcept with priority parentheses of Boolean operators, or when a searched phrase is not known!When to use Quotes and truncationFor free text words ([tiab]) never use quotes and truncate when relevant  Truncation will be ignored in quotesWith mesh terms ([mesh]) always use quotes, and never truncate  Mesh term may be mapped to another termMedische Bibliotheek Erasmus MC 32
  33. 33. How to search systematically?1. What is your research question?2. What elements (key concepts) does the question contain?3. Translate these elements (synonyms, alternatives, abbreviations)4. Combine accoring to set theory (Boolean logic)5. Use the syntax of the chosen database [tw] [tiab] [mesh] Interactive Demo : Red Blood Cells Practically Concurrent! Medische Bibliotheek Erasmus MC 33
  34. 34. Automatic Term Mapping Field Names Based on Entry Terms query is  Manually describe fields in which translated to [MeSH] words should be present between Combined with mesh term and quare brackets exact search words in [All Fields] Translation to MeSH sometime incorrect  Exact translation to the desired MeSH term Use of [All Fields] undesirable  Combined with exact phrasing in title and abstract  Specific MeSH terms exploded or ignored No truncation  Truncation possible Query details much longer than necessary  Query as short as possible Medische Bibliotheek Erasmus MC 34
  35. 35. Dont use Automatic Term Mapping!Conclusion: Automatic Term Mapping is never optimalFor systematic searches always use field names to tell a database exactly what you are looking forHow to prevent Automatic Term Mapping? Always use field names Use (phrase) truncation as much as possible After each synonym (PubMed will only execute ATM when inexperienced users dont use field codes and/or truncation)Keep in mind this automatically reduces the need of quotes, because in this way phrases will be kept together when possibleMedische Bibliotheek Erasmus MC
  36. 36. Field namesKeywords:[mesh] exact mesh term (with all subbranches)[mesh:noexp] exact mesh term (without all subbranches)Free text:[tiab] the exact word or phrase in title or abstractLess frequently used:[sh] subheading (with explode) see furter[pa] pharmacological action (with explode) see furter[nm] Supplementary concepts see furter[pt] Publication type see furterDont use:[majr] en [ti] Due to the lack of relevance sorting you want need to reduce your results to the most relevant ones, with major mesh terms, or free text in the title. Dont use this in systematic literature retrievalMedische Bibliotheek Erasmus MC 36
  37. 37. Keyword Free text Seach for a specific concept  All records contain text, but not all contain Independent of the autors choice of MeSH terms (recent ones) words  Are the additions correct? Search for related terms using the  Concepts not covered by mesh terms, or explode function only recentlyBoth varieties have their pros and cons so when seaching systematicallycombine bothThe safest Method:Look for corresponding MeSH term(s) [mesh]Determine whether to explode these or not [mesh:noexp]Combine in an OR relation with free text words(at least those in entry terms) [tiab] Medische Bibliotheek Erasmus MC 37
  38. 38. Subheadings [sh]If subheadings are about a certain general concept: treat them as a separate elementDont combine MeSH terms and subheadings into one element. You will lose important articles. Add the subheading as an distinct element, with keywords and free text word search. (psoriasis[mesh] OR psoria*[tiab]) AND (etiology[sh] OR etiology[tiab])If an element can only be translated by a combination of MeSH term and specific subheading : treat them as one elementIn this element search for the combination of MeSH and subheading or free text phrases. For instance: alcohol metabolites: (ethanol/metabolism[mh] OR alcohol metabolit*[tiab]) Medische Bibliotheek Erasmus MC 38
  39. 39. Pharmacological actions [pa] (drug types)PAY ATTENTION when looking for drug typesDrug[mesh] added to articles about a drug, drug[pa] added to articles about research that have used this drugThe field Pharmacological actions is not retrieved with [tiab] or [mesh]. Use [pa] additionallyanticoagulants 185322anticoagulant* 194100anticoagulant*[tiab] 38754anticoagulants[mesh] 51966anticoagulants[pa] 179174anticoagulants[mesh] OR anticoagulants[pa] 180671anticoagulants[mesh] OR anticoagulants[pa] OR anticoagulant*[tiab] 195372(OR circulating anticoagulants[nm] 195380)Medische Bibliotheek Erasmus MC 39
  40. 40. Supplementary concept [nm] (Substance Name)Additional to the MeSH terms (25000), extra 140000 supplementary concepts. Not part of the thesaurus tree Contain usually links to the best matching MeSH term(s) Mainly chemical substances (hence the abbreviation nm, substance name), or rare diseases When searching [pa] (pharmacological action) both relevant MeSH terms and supplementary concepts will be searched.Medische Bibliotheek Erasmus MC
  41. 41. Publication type [pt]  Case Reports  Clinical Trial  Comparative Study  Evaluation Studies  Meta-Analysis  Validation Studies Can be used to limit your results to a certain type of publication, but never use it alone, always in combination with free text words Mind this: articles about a certain publication type have the mesh term … as topicMedische Bibliotheek Erasmus MC
  42. 42. Practicum : syntax --- continue with the synonyms provided by the workshop leader ---7. Combine the synonyms the workshop leader found into correct PubMed syntax a. Add field names. - [mesh] or [mesh:noexp] - [tiab] - If necessary use [sh], [pa], [nm] or [pt] additionally a. Use (phrase) truncation to reduce the number of synonyms necessary mentioned b. Can you search phrases as real phrases (remember you want to be exhaustive, so you need to include all possible phrases) or is it wiser to split some phrases into an AND combination? Dont you get too many noise? c. Add parentheses around elements to group synonyms d. Use boolean operators AND between elements and OR between synonyms in an element (don’t use NOT) Medische Bibliotheek Erasmus MC 42
  43. 43. How to search systematically?1. What is your research question?2. What elements (key concepts) does the question contain?3. Translate these elements (synonyms, alternatives, abbreviations)4. Combine accoring to set theory (Boolean logic)5. Use the syntax of the chosen database6. Execute the query - paste multiple lines in search details or advanced > edit7. Analyse the results - check for errors - too much / too little results / are the results relevant? - do you spot additional words/phrases you havent included in your search yet?  optimization Medische Bibliotheek Erasmus MC 43
  44. 44. Analyse the results: check for errorsHow do you know an error occurredToo often: NOT!Sometimes: Too many or too little hits (than expected)Check you query for mistakesGo to Search details and use Ctrl-F to searchFrequent mistakesPhrase unknown or all fields Every instance is one too manyField code missingOR missing AND odd frequency is wrong check if ANDs are deliberateMissing parentheses PubMed only checks the total number of opening and closing parentheses. Split the query in elements to check eachelement.Medische Bibliotheek Erasmus MC
  45. 45. Analyse the results: too much / too littleWhat is too much what is too little.No clear borders!Dependent on the time and effort you want to investDependent on the goal of your research (systematic review or thesis ormore general)Sometimes 50 is enough, sometimes 5000 is too little.When can you stop?If adding extra words or dropping elements doesn’t add any extrarelevant items.What words should you add then? Those present in the alreadyretrieved articles that are synonyms of your elements. optimizationMedische Bibliotheek Erasmus MC
  46. 46. Basic optimization of your resultsAlways:1. Pay close attention to mesh terms or free words/ phrases that combine two elements in one.2. Solve truncation problems if they appear (one by one!)3. Scan the first relevant hits on synonyms you haven’t included in your search4. Per element: scan the abstracts of articles that have the MeSH terms, but not the free text words already known.5. Per element: Scan the MeSH terms of articles that have these free text words, but not the MeSH terms already known.6. Replace important specific elements with more general ones7. Drop unimportant elements from your query and see what extra articles you found. Medische Bibliotheek Erasmus MC
  47. 47. Number of hits:Elements : optimization 4091(+170%) 1236(+231%) 797 295 1913 (+55%) (-53%) specific generalimportant broccoli cruciferous vegetables cancer subset cancer in PubMed Filter: NOT ((animals[mh] OR plants[mh]) NOT humans[mh]) preventionunimportantMedische Bibliotheek Erasmus MC
  48. 48. Practicum : optimization --- continue with the syntax provided by the workshop leader ---7. Try to solve the problems/ tips addressed by the workshop leader8. Start optimizing your search yourself: a. Solve any truncation problems that occur. b. Can you find new relevant words in the first results? c. What other synonyms can be found in articles have mesh terms for an element, but not those free text words d. And the other way around: what other mesh terms can you find? Medische Bibliotheek Erasmus MC 48
  49. 49. How to search systematically?1. What is it you want to know?2. What elements (key concepts) does the question contain?3. Translate these elements (synonyms, alternatives, abbreviations)4. Combine accoring to set theory (Boolean logic)5. Use the syntax of the chosen database6. Execute the query7. Analyse the results8. Adapt the query to other databases - change the syntax - compare other keyword systems and synonyms - check those results on relevancy and other words9. Repeat until you are satisfied (but dont be satisfied to easily) Medische Bibliotheek Erasmus MC 49
  50. 50. When are you done optimizing?When you checked all of these methods and adding extra words does not add extra relevant articles to your resultsetWhen all previously known items by you, or by other (systematic reviews on the same topic) have been found You’ve reached a fair point of exhaustivenessNever overestimate what you can do when searching! You will always miss articles, because:• Bad, short or missing abstract• Published in smaller foreign journals (especially negative results)• Unpublished worksSo if you want to be exhaustive always use other methods:• Hand search key journals• Ask experts in the field (use Scopus)• Check reference lists from key articles (use EndNote & Scopus)How much searching is enough? Comprehensive versus optimal retrieval for technology assessments Andrew Booth International Journal of Technology Assessment in Health Care 26 (4) 431-5 Medische Bibliotheek Erasmus MC
  51. 51. Advanced tips en tricks Finding a specific article Medische Bibliotheek Erasmus MC 51
  52. 52. Try to find this article in PubMed:Fortes C, Mastroeni S, Melchi F, Pilla MA, Antonelli G,Camaioni D, Alotto M, Pasquini P. A protective effect of theMediterranean diet for cutaneous melanoma. Int J Epidemiol.2008 Oct;37(5):1018-29. 10 1 2 3 4 5 6 7 8 9Medische Bibliotheek Erasmus MC 52
  53. 53. What is the PMID?Medische Bibliotheek Erasmus MC 53
  54. 54. Try to find this article in PubMed:Fortes C, Mastroeni S, Melchi F, Pilla MA, Antonelli G,Camaioni D, Alotto M, Pasquini P. A protective effect of theMediterranean diet for cutaneous melanoma. Int J Epidemiol.2008 Oct;37(5):1018-29.Medische Bibliotheek Erasmus MC 54
  55. 55. What is the PMID?Fortes 1018 : 18621803Medische Bibliotheek Erasmus MC 55
  56. 56. Try to find this article:Jones RB, OConnor A, Brelsford J, Parsons N, Skirton H.Costs and difficulties of recruiting patients to provide e-health support: pilot study in one primary care trust. BMCMed Inform Decis Mak. 2012 Mar 29;12:25.Medische Bibliotheek Erasmus MC 56
  57. 57. What is the PMID?jones 25 : 6492 hitsMedische Bibliotheek Erasmus MC 57
  58. 58. What else could we pick easily?Jones RB, OConnor A, Brelsford J, Parsons N, Skirton H.Costs and difficulties of recruiting patients to provide e-health support: pilot study in one primary care trust. BMCMed Inform Decis Mak. 2012 Mar 29;12:25.Medische Bibliotheek Erasmus MC 58
  59. 59. Try this!Jones RB, OConnor A, Brelsford J, Parsons N, Skirton H.Costs and difficulties of recruiting patients to provide e-health support: pilot study in one primary care trust. BMCMed Inform Decis Mak. 2012 Mar 29;12:25.Medische Bibliotheek Erasmus MC 59
  60. 60. What is the PMID?jones 25 2012 : 712 hitsBut:jones[1au] 25[pg] 2012[dp] : 22458706Medische Bibliotheek Erasmus MC 60
  61. 61. Advanced tips en tricks Finding a specific article Solving truncation problems Find free text words and mesh terms in relevant items or their related references using pubreminer (and hubmed to collect related articles) Find phrases not known to but present in pubmed using google Medische Bibliotheek Erasmus MC 61
  62. 62. Disadvantages of PubMed1. Limited truncation options (600 variants, no wildcard)2. Strange behavior when truncating phrases (longer wordstem often retrieves more results)3. No proximity operators If you want to be more precise every possible phrase should be written out, but:3. Not all phrases that are present in articles are known and searchable in PubMed4. No relevance ranking PubMed is not optimal for performing systematic searches.We recommend searching other databases (as well)Embase.com contains almost all PubMed articles, plus several others, can do relevance ranking, better truncation and has real proximity operators Medische Bibliotheek Erasmus MC 62
  63. 63. Summarized1. Start your search in a MS Word Document2. Divide your research question into elements3. Open the MeSH database and try to find the best MeSH terms for each element4. For those MeSH terms use at least the entry terms as free text searches and paste them in Word5. Use one of the field names [mh] and [tiab] ([pa] [nm] [pt] [sh]) for all synonyms of all elements, use parenthesis and OR to combine synonyms into elements, and combine all elements with AND6. Only after you translated all important elements this way, open the PubMed database and search for articles7. Optimize your search until you are satisfied (use the roadmap) If you really want to be exhaustive do the workshop on multiple databases Medische Bibliotheek Erasmus MC 63
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