Copyright © 2020 pubrica. All rights reserved 1

What is a Systematic Literature Search of Multiple Databases

Dr. Nancy Agens, Head,

Technical Operations, Pubrica

sales@pubrica.com

In Brief

Systematic literature search requires to

organize and confront the search process

in a structured manner. Systematic

literature search has a higher chance of

avoiding differences and bias in a

systematic review. The performed use of

multiple databases for a systematic

literature search is the following four

databases, which are EMBASE, Web of

Science Core Collection, MEDLINE, and

Google Scholar.

I. INTRODUCTION

A systematic literature search is a

process of searching literature in a

structured and pre-planned manner, and it

is considered to be a critical component of

the review process as it demands careful

consideration of search terms (See Table

1), selection of databases, systematic

search studies, and the process requires to

reflect on the search findings obtained

during the process. Systematic search

studies are aimed at identifying a

transparent report of the research, and this

process can make the readers know about

the review, what was done to determine

the report and how the collected evidence

supports the systematic review. The

primary advantage of using a systematic

literature review has a higher chance of

avoiding bias, and as well the process

allows in enabling to identify the literature

gaps in the primary or existing research.

Thus, through preventing the risk of bias,

the search studies become reproducible. To

clearly understand this process, in a

systematic review methodology section,

the authors will list all the citations and

databases used for collecting evidence

such as PubMed, Web of Science, Embase

and the journals that were used for

systematic literature search.

II. SELECTION OF RELEVANT

DATABASES

After choosing keywords for a systematic

search study, now the author has to select

the appropriate databases that give relevant

research studies to the formulated

question.

See Also: What is the formulation of the

research question in systematic review? There are a couple of different databases

and search tools available for literature

search, and at this point, it is always good

to search in multiple databases that can

supplement each other. The different

databases include

Bibliographical databases: This

database will have everything about a

topic, a person, a geographical area,

institution, etc.

Library databases: It reflects what

can be physically and electronically

found through one or more libraries.

Journal databases: This database is

commonly consisting of published

journals from a specific supplier.

Specialized databases: This database

will have grey literature, conference

papers, compositions, OA repositories,

artefacts, etc.

Another critical point is to focus on the

subject area, rather than considering the

physical location and the form of data and

the author probably know the extensive

databases within the subject area. Still, it is

advised to check the data provided by the

individual databases, so that the author

can be aware of the database has a bias

towards geographical literature difference.

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To avoid such bias, the author need

answers for the question includes

Are there limitations concerning

different regions or languages, e.g.

French, German, Russian, etc.

covered?

Does the database has covered the past

enough for your purposes?

How quickly does the database gets

updated regarding the registration of

the recent literature?

Does the database cover all the

journals types, e.g. original research

publications, rapid communication,

review articles, and case studies, that

are required?

III. SELECTION OF KEYWORDS THAT

SHOULD BE USED FOR THE SEARCH

While making the selection of appropriate

keywords for search strategy, it is not

mandatorily required to use all the words

from the formulated research question, and

less essential words from the question can

be removed from the search strategy to

avoid unnecessary complications.

Fig. 1: Schematic diagram for determining the optimal order of elements

With the help of Fig. 1 keyword can be

ordered by the importance and their

specificity on a question to determine the

best search strategy. By using this

principle in choosing the keywords, for

instance, keywords can be rated between

specific and important to general and

unimportant, as the rated keyword can be

incorporated in the search strategy. Thus

the general and unimportant keywords

help in avoiding bias and overlapping

elements.

IV. A SEARCH OF MULTIPLE

DATABASES

In general, combined, or multiple database

searches are defined as the search study

across multidisciplinary reporting that

carries its advantages, and it is for studies,

mainly if your work is interdisciplinary.

But it is highly recommended to use of

multiple databases along with added

search strategies (like developing search

terms, controlled vocabulary terms, search

Copyright © 2020 pubrica. All rights reserved 3

fields, phrase searching, search limits and

making search syntax for different

databases) to search relevant references for

conducting a systematic review. A

thorough search is mandatory to identify a

large number of pertinent references which

is necessary for a quality systematic

review. The primary registries of

systematic review recommend using a

different database for investigating. The

Cochrane Handbook suggests using at

least Cochrane Central, MEDLINE and

EMBASE, to search randomized

controlled trials. Whereas, the Cochrane

Collaboration guidelines, a systematic

literature search should include all the

research articles that match the eligible

criteria irrespective of the language,

sample size and journal influence.

See Also: What is a Systematic Review?

It is now clear that a comprehensive search

should consist of multiple databases such

as EMBASE, Medline, Ovid, Cochrane

Controlled Trials Register, Google

Scholar, Scopus and when appropriate to

topic CINAHL (EBSCOhost), PsycINFO

(Ovid), and Sport Discus (EBSCOhost)

can be included. The registries also

advised considering some grey literature to

reduce the publication bias and websites,

such as the World Health Organization

International Clinical Trials Registry

Platform be searched in finding relevant

ongoing and recently completed studies.

However, few works of the literature

suggest that using multiple databases can

be time-consuming and vigorous owing to

the database-specific search strategies

(such as choosing database-specific search

terms, searching with keywords, searching

for exact phrases, searching with subject

headings and citation searching) and

differences subject areas and proximity

operators between interfaces.

The advantage of multiple literature

searches is that it can easily cover an

extensive range of literature and it can also

be perfect in the initial phases of your

searching to find the suitable databases for

your subject area. Whereas the

disadvantage is that the precision in the

searches suffers to some extent as it cannot

use the individual database‘s specialized

search fields and specified subject terms.

Moreover, it is the different vocabulary

terms between databases that may obstruct

translation and limited access, and

subscriptions make the process more

tedious and challenging.

V. VARIATIONS IN SEARCH TERMS

During the search process, variations in

search terms such as truncation, spelling

differences opposites and abbreviations

will be very helping in getting all the

relevant search results. For example,

truncation allows the researcher to search

for words like therap* will thus retrieve

therapy, therapeutic, therapies, etc. Every

database contains a reference to published

articles using both American and British

English spellings, and many interfaces

offer a particular word with a character to

get related search results. For example,

―paediatric‖ or ―pediatric‖ can be searched

as ―p?ediatric.‖

PubMed Ovid EBSCOhost Embase.co

m

ProQuest

Title/abs

tract

[tiab]1 ().ab,ti. TI () OR AB

()2

():ab,ti AB,TI()

All fields [All Fields] .af. 2

3 ALL

Copyright © 2020 pubrica. All rights reserved 4

Thesaur

us term

[mesh:noexp] …/ MH ―…‖ ‗…‘/de MESH(…)

Includin

g

narrowe

r

[mesh] exp …/ MH ―…+‖ ‗…‘/exp MESH#(…)

Combine

d

subheadi

ng

…/sh[mesh] exp …/sh MH ―…+/sh‖ ‗…‘/exp/dm

_sh4

MESH(…

LNK ..)

Free

subheadi

ng

[sh]5 .xs. or .fs.

5 MW :lnk

5

Publicati

on type

[pt]6 .pt. or

exp …/7

PT :it6 RTYPE

Proximit

y

6 ADJn Nn NEAR/n-

NEXT/n

N/n

Exact

phrase

―double quotes‖ No quotes

needed

―double

quotes‖

‗single

quotes‘

―double

quotes‖

Truncate

d phrase

Use-hyphen* No quote* No quote* ‗single

quote*‘

―Double

quote*‖

Truncati

on

End End/ mid End/ mid End/ mid End / mid /

start

Infinite * * or $ * * *

0 or 1

characte

r

— ? # — $1

1

characte

r

— # ? ?8 ?

Added to

database

since

yyyy/mm/dd:yyy

y/mm/dd

[edat]9 (or

[mhda])

limit #N to

rd=yyyym

mdd-

yyyymmd

EM

yyyymmdd-

yyyymmdd

[dd-mm-

yyyy]/sd

LUPD(yyyym

mdd)

Copyright © 2020 pubrica. All rights reserved 4

d10

Publicati

on

period

(years)

yyyy:yyyy[dp] limit #N to

yr=yyyy-

yyyy11

PY yyyy-

yyyy

[yyyy-

yyyy]/py

YR (yyyy-

yyyy)

Record

sets

#1 111

S1 #1 S1

Table 1: Field codes for biomedical literature search in top used interfaces (Obtained from

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6148622/)

VI. TRANSLATION BETWEEN

DATABASES

Multiple database search had to be done to

retrieve as many relevant references as

possible and translating complicated and

exhausting findings between databases will

be time-consuming and burdensome. To

overcome that burden and save time,

Erasmus University Medical Center

developed to find and replace method for

biomedical and health science questions.

Using the five different macros, a search

can be translated relatively quick into eight

significant databases, and the dotted lines

represent databases that are used in less

than 80% of the searches.

Fig. 2: Schematic representation of translation between databases (Obtained from

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6148622/)

In summary, a systematic review uses

scientific methods in finding results from

multiple primary research studies and a

combination of various databases would

Copyright © 2020 pubrica. All rights reserved 4

yield more publication journals than using

an individual database, which can help to

make accurate decisions. But there need to

be ways to optimize using multiple

databases and combinations to include all

the relevant references in the systematic

review. Few literatures suggest using a

combination of databases, depending on

the review topic or the area of research

and majority of the literature states that

searching one database may prove to be

insufficient, thus leading to missing

references.

Pubrica provides support in writing a

systematic review on biomedical or

healthcare areas such as public health

interventions, environmental interventions,

adverse effects, clinical trials, and social

interventions and offers you complete

support across a variety of journals,

publications, and books. Our technical

expert team provides complete support

from translating your concept to incisive

report, and we will be with you through

the entire publication stages.

REFERENCE

1. Levay P, Raynor M, Tuvey D. The contributions of

MEDLINE, other bibliographic databases and

various search techniques to NICE public health

guidance. Evid Based Libr Inf Pract 2015; 10:50–

68.

2. Higgins JPT, Green S. Cochrane handbook for

systematic reviews of interventions: The Cochrane

Collaboration, London, United Kingdom 2011

3. Whiting P, Westwood M, Burke M, Sterne J,

Glanville J Systematic reviews of test accuracy

should search a range of databases to identify

primary studies. J Clin Epidemiol 2018 61:357–364.

DOI:10.1016/j.jclinepi.2007.05.013

4. Higgins JPT GS Cochrane handbook for systematic

reviews of interventions. Version 5.1.0 (updated

March 2011). The Cochrane Collaboration, 2011.

Available at: www.cochrane-

handbook.org/.

5. Bramer WM, Rethlefsen ML, Kleijnen J, Optimal

database combinations for literature searches in

systematic reviews: a prospective exploratory study.

Syst Rev 2017; 6(1):245.

6. Wichor M. Bramer., et al., A systematic approach to

searching: an efficient and complete method to

develop literature searches, J Med Libr Assoc. 2018

Oct; 106(4): 531–541.

DOI: 10.5195/jmla.2018.283