Mini-symposium

Has it been done before?

Research

H. L. Halliday

What is already known about the question that you want to answer? Has someone already given the answer, in a little known journal somewhere in the world? How can you find out what has been studied and published? How can you critically evaluate papers to determine if the answers obtained are reliable?

These questions should first be bounced off your senior colleagues, especially those who are known to have good memories and to keep up with the medical literature. Your senior colleague may have acquired photocopies of papers on your subject going back a number of years. Good review articles may be especially useful and often contain key references. It may be helpful to consult colleagues at hospitals or university departments in the UK, Europe or USA. They may tell you about an inhouse publication not yet formally submitted. Registers of ongoing trials are available and should be consulted (Table 1).

Searching the literature

For this you need a good medical library and access to bibliographic databases. Five steps have been suggested to organise a literature search (Table 2).

Table 1 Registers of planned, ongoing or completed trials

Cochrane Database of Systematic Reviews -completed trials

International Registry of Perinatal Trials (IROPT) -planned, ongoing and completed

British Paediatric Association Research Unit - in preparation

British Association of Perinatal Medicine - Perinatal Clinicals Trials Group

-planned and ongoing

Henry L. Ha&day MD, JSRCP, Regional Neonatal Unit, Royal Maternity Hospital and Department of Child Health, Grosvenor Road, Belfast 12, N. Ireland.

Correspondence and requests for offprints to HLH.

Table 2 Five steps needed to organise a literature search

1. Decide on the subject: the topics and how they relate to each other, what terms will adequately represent these topics.

2. Decide on the extent of your search: how wide and how far back your search should go. English language only, or include German, Japanese, French. Extend 5, IO,20 years or more.

3. Decide on whether you will do your own search or will seek help from a professional searcher (Librarian).

4. Decide on the bibliographic databases through which you will search for relevant papers (a professional searcher can offer advice).

5. Decide on how you will record the references from your search.

The subject of the search

The key words and search terms you select to represent the subject and how they relate to each other are of critical importance for an effective search. It is important to try and obtain as complete a review of published work in your area of interest as possible. Writers of reviews have been criticised for selectively citing the literature to support their own viewpoints. Traditional review articles should now be replaced by structured overviews, using meta-analysis techniques to pool information if necessary.

You should start by writing down the topics that make up the subject of your research. Suppose you wish to investigate how effective steroid treatment is in boys with Henoch-Schonlein purpura. You would need to list steroids, corticosteroids, glucocorticoids, boys, males, children, Henoch-Schonlein purpura and nephrotic syndrome. It is important to define precisely your subject taking into account any synonyms, alternative spellings or variation in trans- atlantic terminology. Discussion with a qualified librarian is often helpful at this stage.

Current Paediafrics ( 1994) 4, 149- 15 I

0 1994 Longman Group Ltd 149

150 CURRENT PAEDIATRICS

Tools for the search?

An indispensable tool for researchers is the Index Medicus which should be available in all university hospital libraries. It is published by the National Library of Medicine in the USA and appears monthly. At the end of each year a Cumulative Index Medicus is published bringing together the 12 previous monthly issues in sequence. The annual list of journals covered by the Index Medicus is published each January and contains more than 3500 of the world’s most important medical journals. The list however is not completely comprehensive and import- ant papers published in other journals can be missed.

The next stage is to consult the list of medical subject headings (MeSH) which is also published each January. MeSH, also called the thesaurus, lists all the possible words and groups of words that you may need to cover the topic. The terms listed are American and if you need to check any meanings Dorland’s Illustrated Medical Dictionary, which is the standard work used in the preparation of Index Medicus, should be consulted. If the thesaurus is used correctly with Index Medicus the use of American words and phrases should not be a problem for British users.

An alternative to Index Medicus is Excerpta Medica which is published in Amsterdam and covers about 5000 journals. It also includes abstracts but, unlike Index Medicus, it divides its coverage into several subject sections. This can make it more difficult to use and not all libraries take all the sections. Searching Excerpta Medica is similar to searching Index Medicus. There is a thesaurus (Malimet). The time lag for inclusion of papers is longer than for Index Medicus.

The literature may also be searched by computer, which makes more databases available to you. Manual searching can be slow and boring but may be preferable for single concept searches and it also has the advantage of being free to the searcher.

Online computer search

The procedures are basically similar to those of a manual search but the computer is particularly useful when the subject is complex and extensive. It is much faster, more complete and, because the computer will print the bibliography also, is usually more con- venient. Until recently online searching was carried out only in medical libraries where librarians could help. With the development of personal computers, databases can be accessed from home or your own office. Medical databases were among the first to become available and they were developed from the printed versions of publications like Index Medicus and Excerpta Medica. In the UK major databases are included in BLAISE-LINK, Data-Star and DIALOG (Table 3). BLAISE-LINK is a group of databases provided from the British Library

Table 3 Some medical databases available in UK

MA/SE-LINK Bioethics Health (planning and administration) MEDLINE Toxline

Data-Star BIOSIS Previews BMA press cuttings Current Contents Search DHSS DATA Excerpta Medica MEDLINE SERLINE

DIALOG BIOSIS Previews Child Abuse and Neglect Current Contents Search MEDLINE Medtext

Bibliographic Services Division, but the service actually operates from the computer at the National Library of Medicine in Bethesda. MEDLARS (Medical Literature Analysis and Retrieval System) is the database and computer system and MEDLINE (MEDlars on LINE) contains references to articles in more than 3500 journals. Data-Star is provided by Radio Suisse with Predicasts International Inc. Although both systems include Medline (Index Medicus), the files are arranged in different combi- nations of years (Data-Star 20 years in one go or seven separate searches in BLAISE-LINK).

The cost of an online search includes the initial outlay for the equipment and the running costs of carrying out each individual search. The cost of logging on to the main computer, telephone calls and database royalties could amount to several pounds per minute. Unless you are an experienced searcher you would be well advised to seek help from a skilled colleague or the university librarian.

Files from MEDLINE are becoming available in many libraries on disks of the CD-ROM format (compact disk read only memory). These CD-ROM files reduce the cost of searching and make it easier for novices. The plastic disks are read by a small laser beam and are capable of storing up to 300000 pages of information on one condensed disk. CD-ROM offers the facility to:

?? search for information on a subject or range of subjects

?? browse through titles and abstracts on the screen 0 print out references ?? download onto disk

In some institutions library CDs are networked across the campus so that a disk held in one library can be accessed by a terminal located in another site using JANET (Joint Academic Network). This system allows many more online databases to be available on CD-ROM.

HAS IT BEEN DONE BEFORE? 151

Keeping records of the search

Recording the data obtained from a search is important and each journal has its own rather idiosyncratic referencing system usually either Harvard or Vancouver. Abstracts or papers may be printed in full and kept on file. One way to record references is to use small plain postcards. The title, volume number, authors’ names, inclusive page numbers and date of publication should all be written or typed on these postcards. You should list the main points of interest for each paper on the back of the postcard, for example a quoted incidence of the condition being studied, follow-up results or outcome of a trial of different drug regimens. Data Management Systems are now available for personal computers to allow this information to be collated electronically.

Photocopies of articles may be obtained directly from the local medical library or via the British Library Document Supply Centre, although a charge may be incurred for the latter.

Judging the completeness of the search

This is difficult unless you use more than one source and include both manual and computer searches. You may need to search multiple databases and it may also be necessary to use more than one search strategy on each database in order to cover the subject completely. It has been estimated that elec- tronic searches cover only 30-50% of the existing literature of randomised controlled trials, although there has been an improvement in the past 5 years with the introduction of newer and more comprehen- sive MeSH terms and text words.

Judging the quality of the evidence

Have the published research trials clearly answered the question asked by the researcher? Most studies of treatment use one of five designs which in ascending order of reliability based upon method- ology are:

0 single case reports ?? case series without controls ?? non-randomised studies using historical controls ?? non-randomised studies using concurrent controls ?? randomised controlled trials

The first four trial designs are really forms of observational studies, whereas the fifth is a true experimental study and is the most reliable. Randomised trials can be used to estimate the magnitude of the effect of a medical intervention but the estimate can be imprecise. Precision can be assessed by calculating the 95% confidence interval of the effect measured either as an odds ratio or a relative risk. The clinical significance of a true treatment effect depends upon its size and on the complications and costs of treatment. If a series of small trials fail to show a statistically significant benefit from an intervention, the technique of meta- analysis may be used to increase statistical power. This will provide increased precision in the estimate of effect size (Sinclair & Bracken, 1992). It is often necessary to undertake multicentre randomised trials to obtain adequate sample sizes to demonstrate relatively small but nevertheless important clinical effects of new therapies. Unfortunately these large trials are difficult and expensive to undertake.

Good luck with your searches; maintain a healthy cynicism, a critical mind and aim high.

Acknowledgements

I would like to thank Gaynor Creighton, Librarian at The Queen’s University of Belfast Medical Library, Royal Victoria Hospital, Belfast for her helpful advice.

Further reading

Huth EJ ed. Searching the Literature. In: How to write and publish papers in the medical sciences. 2nd Edition. Baltimore: Williams and Wilkins, 1990, 12-42.

Altman DG. The scandal of poor medical research. BMJ 1994; 308: 283-284.

Kirpalani H, Schmidt B, McKibbon KA, Haynes RB, Sinclair JC. Searching MEDLINE for randomized clinical trials involving care of the newborn. Pediatrics 1989; 83: 5433546.

Sinclair JC, Bracken MB, eds. Effective care of the newborn infant. Oxford: Oxford University Press, 1992. Cochrane Pregnancy and Childbirth Database (Revised from The Cochrane Database of Systematic Reviews). Published through Cochrane Updates on Risk. Oxford: Update Software, 1993, Disk Issue I.

Stephen J. Search the literature. In: How to do it, Vo12 published by the British Medical Association, London, 1987,77782. Stephen J. Carry out an on line search. In: How to do it, Vo12 published by the British Medical Association, London, 1987, 83-88.

Evidence - based medicine working group. Evidence-based medicine. JAMA 1992; 268: 2420-2425.