Literature Review in Medical Research

Dr Arun Prasad K.P

A literature review is the effective evaluation of current knowledge on a research topic.   The “Literature” implies the works you consulted in order to understand and investigate your research problem.

An effective review of medical literature should answer or clarify the following:

  • What we already know – in terms of theory & clinical practice
  • What is lacking
  • Why study the problem – Rationale / Relevance of study
  • What methods to use


  • Searching for information – Sources & method of searching
  • Critical review
  • Documentation
  • People – convenient, easily accessible
  • Text – Traditional / Online – not the most updated, but a starting point
  • Primary / Non appraised sources – Research articles
    • Individual journals – Traditional / Online – are refereed by editorial board, evaluated, up-to-date, but has time lag.
  • Secondary / Pre-appraised sources / Integrative literature – Systematic Review, Meta-analyses etc
    • Individual journals / Books / Sites – Clinical Evidence (BMJ), Cochrane library
  • Grey Literature
    • Theses & Dissertations – inexperienced researchers
    • Conference Proceedings – Latest unpublished research, can identify people involved in research
  • Other – Govt./ NGO reports, Newspaper, Magazines etc

Searching – Sources of Information

Searching – Method
Finding references to articles most important.   References can be found in Text books / Articles / Index or Databases of references

Indexes or Databases of References
Databases – Traditional e.g. Index Medicus or Electronic / Online eg. Medline

Index Medicus

  • Published by US NLM, Started 1879, published monthly, stopped 2004
  • Cumulative Index Medicus – published annually, stopped 2000
  • Maintained by US NLM contain approx 17 million references to > 5000 life sciences journal articles, from 1950-51 to present
  • Indexed by Medical subject headings – MeSH
  • Search can be filtered by Author, Journal, Period, Article type etc more in Advanced search
  • Poor Homoeopathy representation especially English – only BHJ / Homeopathy, JAIH etc
  • Some abstracts, some have free full text archived in PubMed central or free journal sites
  • Clicking on each citation gives abstract, publication type, MeSH terms, Links to full text etc
  • Maintained by Elsevier, comprehensive pharmacological & biomedical database, more European journals, > 80% abstracts
  • Database of Indian biomedical journals – by Indian MEDLARS Centre – setup by NIC and ICMR – Free full text available at

Medline – MEDLARS Online – Medical Literature Analyses & Retrieval System 

EMBASE – Excerpta Medica Database 

IndMED –  

Other – BIOSIS, SIGLE – System for Information on Grey Literature in Europe

Finding Homoeopathic Information- Problems
Scanty homoeopathic information in popular medical databases: e.g. Study by Department of Epidemiology, University of Limburg, Maastricht, NetherlandsKleijnen J, Knipschild P. The comprehensiveness of MEDLINE and EMBASE computer searches. Searches for controlled trials of homeopathy, ascorbic acid for common cold and ginkgo biloba for cerebral insufficiency and intermittent claudication.  Pharm Weekbl 1992;14:316–20

“RESULTS: For homoeopathy, ascorbic acid and ginkgo the proportion of all trials found by Medline was 17%, 36% and 31% respectively and for Embase 13%, 25% and 58% respectively. After checking of the references in the Medline articles 44%, 79% and 76% of all trials were identified. After checking of the references in the Embase articles 42%, 72% and 93% of all trials were identified.”

Finding Homoeopathic Information- Solution – Homoeopathic & CAM Databases

Hom-Inform Database

  • Homoeopathic Library Information Services of British Homoeopathic Library, part of Glasgow Homoeopathic Hospital
  • Database of over 25000 article & book references to Homoeopathy, free to search, some abstracts, photocopies possible


  • Publishes CHLAS – Current Health Literature Awareness Services since 1988 gives citations of scientific articles published in journals subscribed by CCRH
  • Library provides photocopies of selected articles on specific requests
  • Also CCRH Quarterly Bulletin – A Cumulative Index, Theses index etc
  • Plan to launch HOMLINE, similar to Hominform

Provings Database –  – Jeremy Sherr & Archibel

  • More than 1000 new provings listed
  • Search for a proving, using the name of substance, of the proving investigator, the manufacturer, etc. – can also upload your own proving
  • For each proving gives name of investigator, year, contact details, rarely link to proving

HomBRex –

  • Database on Basic Research experiments on Homeopathy – indexes studies on biological systems including animal, human, plant, fungi and microbial organisms. – Needs free registration
  • More than 1190 experiments in more than 900 original articles
  • : A portal  for homoeopathic students teachers and professional

CAM Databases

o   CAMbase –

  • Covers about 80,000 bibliographical records from more than 30 journals on complementary medicine most of them not listed in MEDLINE

User friendly – can type in his request as a naturally spoken phrase

o   AMED –

Allied & Complementary Medicine Database of British Library

Finding a copy
References can be followed up in medical library / online libraries.   Look up abstract to know whether potentially interesting or not.

  • Can obtains articles by subscription at most journal sites
  • Free full text articles online – depends on individual journal policy
  • Free Article collections – , open access publishers like BioMed central –
  • Document delivery services 

Other ways to find relevant information:

  • Personal communication – Contact those who have conducted similar research
  • For dissertations, theses etc. contact colleges / universities
  • Web search with popular search engines or speciality tools like Google scholar (

Critical review of literature

  • For research paper assess
    • Type of study / Relevance to your study / Aims & Objectives / Materials & Methods / Sample size / Statistical Methods / Results & conclusions – whether appropriate
    • Bias or conflict of interest – transparent or  not
    • Peer reviewed articles most credible
    • Details in series of “Users’ guides to the medical literature” in JAMA –
  • Re-organise, reshuffle & summarize as sequentially relevant text
  • Traps to avoid
    • Forgetting the purpose
    • Trying to read everything
    • Reading not writing
    • Not referencing your notes
  • Details of referencing methods at US NLM’s Citing Medicine site –
  • Details of manuscript submission in “Uniform requirements of manuscripts submitted to biomedical journals” published by International committee of medical journal editors

Dr Arun Prasad K.P.   MD (Hom)
Dept of Materia Medica
Govt.Homeopathic Medical COllege, Calicut
Email : [email protected]

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