Chapter 3 · Starting a study

How do you find out what is already known?

Sources of literature, computer-aided search, and organising what you find.

14 TNMGRMU questions answered hereset 16 times, 2013–2025

The problem first

You are a first-year MS Obstetrics and Gynaecology resident. Your thesis will test tranexamic acid for blood loss at caesarean section. You type “tranexamic acid caesarean” into Google, read the first page of results and write in your protocol that “very few studies have been done”.

A structured PubMed search on the same question returns 43 records indexed as randomised controlled trials (search run on 14 September 2026). At the protocol presentation, a committee member asks one question.

“Which databases did you search, with which terms, and on what date?”

Start here

Why search the literature before you start?

A literature search is a planned, recorded search of published and unpublished sources to find out what is already known about your question. Almost every part of a protocol depends on it.

The search tells you whether the question has been answered, and supplies the design, the outcome measures and the numbers for the sample size calculation. The Declaration of Helsinki (2024) requires research to be “based on a thorough knowledge of the scientific literature” and to “avoid research waste”.

Feature	Literature search	Literature review
What it is	Finding and retrieving what has been published or registered on a question	Reading, appraising and summarising what the search found
Output	A list of records, plus the search strategy and dates	The review of literature chapter, or the introduction of a paper
Skills	Choosing databases, search terms and Boolean operators	Critical appraisal, synthesis and writing
Order	Comes first	Follows the search
Formal version	A comprehensive search with a written strategy	A systematic review

Sources of literature

What are the sources of literature?

Sources are grouped by how far they are from the original research. Primary sources report the study itself. Secondary sources collect or summarise primary sources. Tertiary sources are compiled from both.

Texts do not all draw the line in the same place: indexes and guidelines are classed as secondary in some books and tertiary in others. Grey literature is material published outside traditional commercial publishing, such as theses, dissertations, conference abstracts and government reports.

Source	Examples	Use it for
Library print collection	Textbooks, bound journals, theses, the catalogue	Background, older literature, dissertations of your university
Bibliographic databases	PubMed/MEDLINE, Embase, CINAHL	Finding journal articles by subject
Systematic review collections	Cochrane Library	Checking whether the question has already been reviewed
Search engines	Google Scholar	Following citations, finding full text and theses
Trial registries	CTRI, WHO ICTRP, ClinicalTrials.gov	Ongoing and unpublished trials
Thesis repositories	Shodhganga	Indian Ph.D. theses
Grey literature	Government and WHO reports, conference abstracts	Programme data and results not in journals
People	Guides, experts, authors of key papers	Studies that searches miss

Computer-aided search

Which databases should you know?

Each database covers a different set of journals and records. No single one holds everything.

PubMed (National Library of Medicine, USA): free, more than 40 million citations and abstracts of biomedical literature. It does not hold full text but links to it. It has three parts: MEDLINE, citations for PubMed Central (PMC) articles, and Bookshelf.
MEDLINE: the largest part of PubMed. More than 31 million references from more than 5,200 journals in about 40 languages, mainly from 1966 onwards. Its records are indexed with MeSH subject headings.
PubMed Central (PMC): a free full-text archive of articles.
Embase: available only by subscription, from Elsevier or other vendors such as Ovid.
Cochrane Library: contains the Cochrane Database of Systematic Reviews, CENTRAL (reports of randomised and quasi-randomised trials) and Cochrane Clinical Answers.
CINAHL: an index of nursing and allied health journals.
Google Scholar: journal papers, theses, books, preprints, abstracts, court opinions and patents from all subjects. It ranks results by the full text, where and by whom a paper was published, and how often and how recently it has been cited.
Clinical Trials Registry – India (CTRI): free and searchable, launched on 20 July 2007 by ICMR, and a primary registry in the WHO registry network. The WHO ICTRP search portal links registries in that network.
Shodhganga (INFLIBNET): open-access repository of Indian Ph.D. theses. It crossed 6,00,000 theses on 7 May 2025.
One Nation One Subscription (ONOS): from 1 January 2025, access to more than 13,000 journals from 30 international publishers for government higher education and research institutions.

Feature	PubMed	Google Scholar
Content	Citations and abstracts of biomedical and life-science literature	Scholarly papers from all subjects, plus theses, books, preprints, court opinions and patents
Subject headings	MeSH on MEDLINE records	None
Search control	Field tags, AND/OR/NOT, brackets, Search Details, filters	Few operators, such as author:, and at most 1,000 results per query
Can the search be repeated exactly?	Yes: the full strategy can be reported	Not reliably. Gusenbauer and Haddaway (2020) found it unsuitable as the main search system for systematic reviews
Best use	Structured topic searches	Citation chasing ("Cited by"), full-text links, theses

Building the search

How do you turn a question into search terms?

Split the question into its concepts, list every word authors use for each concept, and combine them.

The usual structure is PICO: Patient or Population, Intervention, Comparison, Outcome, described by Richardson and colleagues in 1995 as the “well-built clinical question”. The Cochrane Handbook advises that a search usually has three sets of terms: the condition, the intervention and the study design. Synonyms inside a set are joined with OR, and the sets are joined with AND.

The question from the problem above, as a PubMed search. Bar lengths use a log scale, because counts range from 43 to more than 3 lakh. Typed as plain words, “tranexamic acid caesarean section” found 233 records. The structured P AND I string found 298. Adding the outcome block removed 32 records, so check that it does not exclude papers that describe blood loss in other words.

The full string for P AND I AND O, restricted to trials:

("Cesarean Section"[mh] OR caesarean[tiab] OR cesarean[tiab]) AND ("Tranexamic Acid"[mh] OR "tranexamic acid"[tiab]) AND ("Postpartum Hemorrhage"[mh] OR "Blood Loss, Surgical"[mh] OR "blood loss"[tiab] OR haemorrhage[tiab] OR hemorrhage[tiab]) AND randomized controlled trial[pt]

Boolean operators

What do AND, OR and NOT do to the results?

AND narrows the search. OR widens it. NOT removes records. They are called Boolean operators after the English mathematician George Boole.

I = tranexamic acid block, P = caesarean block, PubMed counts on 14 September 2026. The OR count (1,09,228) equals 99,821 + 9,705 − 298: records in both circles are counted once. Use NOT with care, because it also removes papers that mention the excluded term only in passing.

PubMed rules from its user guide:

Type AND, OR and NOT in capitals. Words typed side by side are combined with AND.
PubMed processes a search from left to right. Put each concept in brackets.
"double quotes" search a phrase. vaccin* finds vaccine, vaccination and other endings. At least 4 letters must come before the asterisk.
Field tags limit a term to one field: [tiab] title or abstract, [au] author, [mh] MeSH heading, [pt] publication type.
Search Details, under Advanced search, shows how PubMed translated your search. Read it before trusting a count.

Interactive

Combine search terms with AND, OR and NOT and watch which records are retrieved

Try this: change AND to OR and watch the count rise from 18 to 76. Then add a third term and move the brackets.

Term 1

Operator

ANDORNOT

Term 2

Add a third term

tranexamic acid AND caesarean

18of 122 records retrieved

tranexamic acid AND caesarean: records that contain both terms = 18.

Teaching example: 122 made-up records. Each dot is one record. Filled red dots are the records the search retrieves.

Controlled vocabulary

Why does PubMed find papers that do not use your words?

Because MEDLINE records are tagged with MeSH (Medical Subject Headings), a controlled vocabulary produced by the National Library of Medicine. One heading covers all the words authors use for the same concept.

MeSH headings are arranged in 16 categories and up to 13 levels, from general to specific. A [mh] search includes the narrower headings below the term. [mh:noexp] turns this off. Synonyms such as “heart attack” are entry terms, and PubMed's automatic term mapping adds the heading for you.

Feature	Text word search	MeSH search
Searches	Words the authors wrote, e.g. in the title or abstract [tiab]	Subject headings added to MEDLINE records [mh]
Spellings and synonyms	Each must be listed: caesarean[tiab] 28,545, cesarean[tiab] 60,567	One heading covers them: "Cesarean Section"[mh] 58,462
Narrower topics	Not included	Included automatically
New citations	Found at once	Missed until indexed. Preprints and online-ahead-of-print citations may have no MeSH
Use	Combine both with OR inside each concept	Combine both with OR inside each concept

The formula

How many results should a good search return?

That depends on what you need. A search can find nearly all relevant papers and bring many irrelevant ones, or bring few irrelevant ones and miss some relevant papers.

Teaching example with made-up numbers. The same database holds 40 relevant papers (red dots). Each grey dot stands for 10 irrelevant records retrieved. A wider search finds more of the 40, and you read more irrelevant records to find them.

Sensitivity = relevant records retrieved ÷ all relevant records

Precision = relevant records retrieved ÷ all records retrieved

Number needed to read (NNR) = 1 ÷ precision

Sensitivity: also called recall: how much of the relevant literature the search found
Precision: how much of what you retrieved is relevant
NNR: records you read, on average, to find one relevant paper

Search A: 38 ÷ 40 = 95% sensitive, 38 ÷ 438 = 8.7% precise, NNR = 1 ÷ 0.0868 = 11.5

Search B: 25 ÷ 40 = 62.5% sensitive, 25 ÷ 55 = 45.5% precise, NNR = 1 ÷ 0.4545 = 2.2

The Cochrane Handbook tells systematic reviewers to maximise sensitivity while aiming for reasonable precision. It notes that abstracts can be screened at about 60–120 per hour. For a quick clinical answer, a precise search is enough. PubMed Clinical Queries offers built-in filters for therapy, diagnosis, etiology, prognosis and clinical prediction guides, each in a broad (sensitive) or narrow (specific) version.

Interactive

Add search terms and filters and watch sensitivity and precision change

Try this: tick cesarean[tiab] and watch sensitivity rise from 37.5% to 92.5%. Then tick AND random*[tiab] and watch precision.

Teaching example with made-up records. Every record matches the tranexamic acid block. The relevant records are the 40 randomised trials of tranexamic acid at caesarean section that report blood loss.

Caesarean concept: terms joined with OR

caesarean[tiab]

British spelling, in the title or abstract

cesarean[tiab]

American spelling, in the title or abstract

"Cesarean Section"[mh]

MeSH heading: covers both spellings, misses citations not yet indexed

Added to the search with AND

AND blood loss block

("blood loss"[tiab] OR haemorrhage[tiab] OR hemorrhage[tiab])

AND random*[tiab]

Finds randomised, randomized, randomly and other endings

(caesarean[tiab]) AND ("Tranexamic Acid"[mh] OR "tranexamic acid"[tiab])

37.5%sensitivity: 15 of 40 relevant trials found

15.0%precision: 15 of 100 records retrieved are relevant

6.7number needed to read

Sensitivity = 15 ÷ 40 = 37.5% · Precision = 15 ÷ 100 = 15.0% · NNR = 1 ÷ precision = 100 ÷ 15 = 6.7

Relevant trials missed: 13 trials that write "cesarean", 3 new trials that write "cesarean" and are not yet indexed with MeSH, 6 trials that write "bleeding" instead of blood loss, 3 trials that write "C-section" in the title and abstract.

What databases miss

Is a database search enough?

No. Papers are also found by following references, by searching registries and grey literature, and by asking people who know the field.

Backward citation searching reads the reference list of a key paper. Forward citation searching finds later papers that cite it, through “Cited by” in Google Scholar or a citation index. PubMed's “Similar articles” compares words in the title, abstract and MeSH terms.

In a review of complex evidence with 495 primary sources, Greenhalgh and Peacock (2005) found that only 30% came from the planned database and hand searches. 51% came from following references of references, and 24% from personal knowledge or contacts.

Bramer and colleagues (2017) studied 58 systematic reviews. 16% of the included references were found in only one database, and Embase gave the most unique references. Embase, MEDLINE, Web of Science and Google Scholar together reached 98.3% recall.

Decide

Where should you search first?

Answer one or two questions about what you need.

What do you need from the search?

Where to search: all possible answers

Tertiary, then secondary sources: Read a recent textbook chapter for the basics, then a recent systematic review. Take your search terms from them.
PubMed, then the Cochrane Library and Google Scholar: Build a PICO search string in PubMed with MeSH terms and text words. Check the Cochrane Library for an existing review. Use Google Scholar to follow citations.
PubMed plus the database of that field: For nursing and allied health, add CINAHL if your library subscribes to it.
Databases plus reports outside journals: Much programme evidence is in government and WHO reports (grey literature). Search those websites as well as PubMed, and record which sites you searched and when.
Several databases, registries and grey literature: Cochrane reviews search at least CENTRAL, MEDLINE and Embase (if available), plus trial registries, reference lists and grey literature. Report every strategy and the date of each search.
Trial registries: CTRI for trials in India, the WHO ICTRP search portal, and ClinicalTrials.gov.
Shodhganga: The INFLIBNET open-access repository of Ph.D. theses submitted by Indian research students. For MD and MS dissertations, ask your university library.
PubMed citation sensor: Paste the title, or the author, journal and year, into the PubMed search box. No field tags or Boolean operators are needed.

Organising literature

How do you organise what you find?

A search for a thesis can return hundreds of records. Without a system, you lose papers, cite them wrongly, or read the same paper twice.

Reference managers

Zotero: free and open source, a project of the Corporation for Digital Scholarship. It saves references from web pages, and lets you organise and tag them.
Mendeley: a free reference manager from Elsevier. It imports PDFs and supports shared group libraries.
EndNote: a commercial reference manager from Clarivate, with retraction alerts while you write.

Each one stores references, inserts citations into a Word document, and builds the reference list in the style your university or journal needs. Check the output: automatic formatting can get capitals, abbreviations and author names wrong. See Writing and referencing for Vancouver style.

A literature matrix

Author, year	Setting	Design, n	Intervention and comparison	Outcome and result	Limitations	Theme
one row per paper	country, hospital	RCT, 120	drug vs placebo	blood loss, with the numbers	not blinded	efficacy

Sort the matrix by theme, by design or by year. Write the review theme by theme, comparing the studies under each theme, instead of summarising one paper per paragraph.

Keep the search current

Save the search strings with the date each was run.
In PubMed, “Create alert” emails new results for a saved search (needs a free My NCBI account). Google Scholar offers email alerts as well.
Before you write the discussion, run the searches again and check whether any paper you cite has been retracted. PubMed lists “Retracted Publication” as a publication type.

Computer applications

Where do computers help in research and practice?

At every stage from the literature search to publication, and in most parts of hospital work.

Data collection software such as REDCap (Research Electronic Data Capture, developed at Vanderbilt University) builds electronic case forms for research data. Statistical software is covered in Choosing a test.

In medical practice, computers hold electronic health records and hospital information systems, run laboratory and imaging systems, check prescriptions for drug interactions, monitor patients in intensive care, and support teleconsultation. In India, the Telemedicine Practice Guidelines were issued on 25 March 2020 by the Board of Governors in supersession of the Medical Council of India.

The library

What does a medical library do for a researcher?

It buys and organises information, helps you find it, and gives you access to what you cannot buy yourself.

Acquisition: selects and buys books, journals and electronic resources.
Organisation: classifies and catalogues them, with an online catalogue.
Circulation: lends books and manages reservations and returns.
Reference service: librarians answer queries and help plan searches.
Electronic access: database and journal subscriptions, including consortia, with on-campus or remote access.
Document delivery and inter-library loan: obtains papers the library does not hold.
Current awareness: informs readers of new publications in their field.
Training: teaches database searching, reference managers and citation.
Repository and archive: keeps the institution's theses and publications.
Academic integrity: provides plagiarism-check software.

S.R. Ranganathan's The Five Laws of Library Science (1931) sets out five laws for a library. Books are for use. Every reader his book. Every book its reader. Save the time of the reader. The library is a growing organism.

By specialty

Literature search problems by specialty

A thesis on vitamin D in type 2 diabetes. Papers use "vitamin D", "cholecalciferol", "ergocalciferol" and "25-hydroxyvitamin D".

List every name authors use for your concept, join the names with OR, and add the MeSH heading.

Common myths

Common mistaken beliefs

Myth: Google Scholar is enough.
It shows at most 1,000 results per query and cannot run a long Boolean strategy that others can repeat exactly. Gusenbauer and Haddaway (2020) found it unsuitable as the main search system for systematic reviews. Use it alongside PubMed.
Myth: PubMed gives you full-text articles.
PubMed holds citations and abstracts. Full text comes through links to the publisher or PubMed Central.
Myth: Lower-case "and" and "or" work as operators in PubMed.
The PubMed user guide says to type AND, OR and NOT in capitals, and to use brackets because searches run from left to right.
Myth: Ticking an age filter keeps every relevant paper.
Age and sex filters depend on MeSH indexing. Citations not yet indexed, such as preprints and online-ahead-of-print papers, are left out.
Myth: The search is done once, at the start of the thesis.
Run it again before writing the discussion. PRISMA 2020 asks for the date each source was last searched.
Myth: A reference copied from another paper's list is safe to cite.
Read every paper you cite. A copied reference can carry the other author's errors, and the paper may not say what you cite it for.

Why this matters to you

Five consequences of a poor literature search

Protocol sent back
The committee asks what is already known, and where your sample size numbers came from.
A thesis on a settled question
Two years spent on a question that trials or a systematic review had already answered.
A viva question you cannot answer
"Which databases, which terms, which date?" "I searched Google" is not an answer.
Papers read uncritically
If you do not know the literature, you cannot tell when an introduction cites only the studies that agree with the authors.
Patients treated on older evidence
Missed trials mean conclusions, and the treatment decisions based on them, rest on incomplete evidence.

History

History of literature searching

1854
George Boole
Published An Investigation of the Laws of Thought, an algebra of logic. AND, OR and NOT in database searching are called Boolean operators after him.
1879
US National Library of Medicine
Began publishing Index Medicus, a printed index of medical articles.
1931
S.R. Ranganathan
Published The Five Laws of Library Science.
1960
National Library of Medicine
Introduced Medical Subject Headings (MeSH), replacing a subject heading list first published in 1954.
1971
MEDLINE
NLM began online access to Index Medicus content (MEDLARS onLINE), covering citations from 1966.
1993
Cochrane
Established in Oxford to prepare systematic reviews of randomised controlled trials, named after Archie Cochrane.
1995
Richardson, Wilson, Nishikawa and Hayward
Described "the well-built clinical question", the source of the PICO structure.
1996–97
PubMed
MEDLINE became searchable through the internet. NLM gives 1996 for public availability and 1997 for the launch.
2004
Google Scholar and Index Medicus
Google launched Scholar in November. The print Index Medicus stopped.
2007
CTRI
The Clinical Trials Registry – India was launched on 20 July.
2021
PRISMA 2020 and PRISMA-S
Updated reporting guideline for systematic reviews, and a 16-item extension for reporting the literature search.
2025
One Nation One Subscription
From 1 January, government institutions in India gained access to more than 13,000 journals from 30 publishers.

Guidelines

Literature searching in guidelines

Declaration of Helsinki (2024), paragraph 21

Research “must conform to generally accepted scientific principles, be based on a thorough knowledge of the scientific literature, other relevant sources of information, and adequate laboratory and, as appropriate, animal experimentation.”

PRISMA 2020, items 6 and 7

Item 6: “Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted.” Item 7: “Present the full search strategies for all databases, registers and websites, including any filters and limits used.”

PRISMA-S (2021)

A 16-item checklist for reporting the literature search of a systematic review, so that each part of the search can be reproduced.

Cochrane Handbook v6.5.1, chapter 4 (MECIR)

CENTRAL, MEDLINE and Embase (if available) should be searched for all Cochrane reviews. Trials registers should also be searched. Reviewers should search grey literature such as reports, dissertations, theses and conference abstracts, and check reference lists of included studies and relevant systematic reviews.

Steps

Doing a literature search, step by step

Write the question in PICO form.
For each concept, list synonyms, both spellings, abbreviations and the MeSH heading.
Join synonyms with OR inside each concept, and join concepts with AND.
Run the search in PubMed, read Search Details, and check that key papers you already know appear.
Search the Cochrane Library, Google Scholar and any database for your field. Then search CTRI or ICTRP, and Shodhganga.
Follow the references of key papers backward and their citations forward.
Export everything to a reference manager, delete duplicates, and record the counts and dates.
Screen titles and abstracts, then full texts, and record reasons for exclusion.
Read and appraise the included papers and enter them in a literature matrix.
Set alerts, and run the searches again before writing up.

Reading a paper

Five checks on any paper's literature search

Which databases and registries were searched, and on what date?
Is the full search strategy given, with any filters and limits?
Were reference lists, trial registries and grey literature searched?
Were language or date limits used, and is the reason given?
Does the introduction cite recent studies, including those that disagree with the authors?

Why is it called that?

Word surgery

“Literature”

In everyday speech

Novels, poetry and plays.

In research

Everything written on a subject: journal articles, theses, reports and registry records.

“Review”

In everyday speech

An opinion on a film or a product.

In research

A summary and appraisal of the studies on a question. A systematic review follows a written method that others can repeat.

Memory trick

OR inside a concept makes the list longer. AND between concepts makes it shorter.

Literature

Latin litteratura: "writing formed with letters", from littera, "letter"

In research, the whole of the writing on a subject.

Research

Old French recercher: "seek out, search closely"

A close, organised search for an answer, which starts with a search of what is already known.

Bibliography

Greek biblion "book" + graphos "written"

A list of books and papers on a subject, or the list at the end of your thesis.

Index

Latin index: "forefinger", anything which points out

A list that points to where information is found. Index Medicus pointed to medical articles.

Thesaurus

Greek thesauros: "treasure, storehouse"

NLM calls MeSH a thesaurus: a controlled vocabulary of headings arranged in a hierarchy.

Boolean

named after George Boole (1815–1864), English mathematician

Logic using AND, OR and NOT, used to combine search terms.

Citation

Latin citare: "to summon, call"

A reference that calls another paper into your text as a source.

Library

Latin liber: "book", originally the inner bark of trees

A collection of books and other information, organised so that readers can find what they need.

Exam answers

Model answer outlines

Literature search: definition, importance and steps (review of literature)

Ph.D. RM 2015, 2016, 2019, 2021

Definition: a planned, recorded search of published and unpublished sources to find what is known on a research question. The review of literature is the critical summary of what the search found.

Importance:

Shows whether the question is already answered, which avoids duplication and research waste (Declaration of Helsinki 2024, paragraph 21).
Identifies the gap and refines the question, objectives and hypothesis.
Guides the design, population, outcome measures and validated tools.
Provides the SD or expected proportion for the sample size calculation.
Warns of problems, adverse effects and biases met by earlier studies.
Needed for protocol approval, the introduction and the discussion. Places your results in context.

Steps:

Frame the question (PICO).
List keywords, synonyms and MeSH headings.
Combine with Boolean operators: OR within a concept, AND between concepts.
Search databases: PubMed/MEDLINE, Cochrane Library, Google Scholar, Embase and subject databases if available.
Search registries (CTRI, ICTRP), theses (Shodhganga) and grey literature. Follow citations backward and forward.
Export to a reference manager, remove duplicates, and record strategies, counts and dates.
Screen, retrieve full text, appraise, tabulate in a literature matrix.
Write by theme, cite in one style, and update the search before submission.

Sources of literature (for a literature review)

Ph.D. RM 2023, 2025

Type	Examples	Features
Primary	Original research articles, theses, conference abstracts, trial registry records	Newest findings and full methods, need appraisal
Secondary	Systematic reviews, meta-analyses, indexing and abstracting databases (PubMed/MEDLINE, Embase, CINAHL)	Locate and summarise primary studies
Tertiary	Textbooks, encyclopaedias, handbooks, formularies	Background and definitions, slower to update
Grey literature	Theses (Shodhganga), government and WHO reports, conference proceedings	Outside commercial publishing, reduces publication bias
Electronic resources	Cochrane Library, Google Scholar, publisher sites, ONOS journals, trial registries	Fast, searchable, often linked to full text
Library	Catalogue, print journals, inter-library loan, librarian help	Access to material you cannot obtain yourself
People	Guides, experts, authors of key papers	Find work that searches miss (24% of sources in Greenhalgh and Peacock, 2005)

Computer-aided search of literature

Ph.D. RM 2013, 2022

Meaning: searching electronic bibliographic databases instead of printed indexes. Index Medicus was printed from 1879 to 2004. MEDLINE went online in 1971. PubMed made it free on the internet in 1996–97.
Databases: PubMed/MEDLINE, Embase, Cochrane Library, CINAHL, Google Scholar, CTRI, WHO ICTRP and Shodhganga.
Frame the question with PICO and list the concepts.
Choose terms: text words and MeSH headings, entry terms and automatic term mapping. [mh] includes narrower headings, [mh:noexp] does not.
Combine: AND, OR, NOT in capitals, with brackets, processed from left to right.
Refine: phrases in quotes, truncation with *, field tags ([tiab], [au], [pt]), filters, Clinical Queries, systematic[sb].
Check and save: Search Details and History, Send to Citation manager, email alerts, Similar articles, “Cited by”.
Judge the search: sensitivity, precision, number needed to read.

Advantages: fast, covers millions of records, combines concepts, can be repeated and reported, sends alerts, links to full text.

Limitations: no database covers all journals, indexing is delayed, skill is needed, some databases need subscriptions, many records are irrelevant, and unpublished studies are missed unless registries and grey literature are searched.

Conducting the literature review and organising retrieved literature (with classification of research designs)

Ph.D. RM 2023, 2024

Conducting the review:

Define the question and scope, and write inclusion and exclusion criteria.
Plan sources, search terms and limits in advance.
Search and record strategies, counts and dates.
Import into a reference manager (Zotero, Mendeley, EndNote) and remove duplicates.
Screen titles and abstracts, then full texts, and record reasons for exclusion.
Appraise each included study for design, bias and relevance.
Extract data into a literature matrix.
Synthesise by theme, noting agreement, conflict and gaps.
Write, citing consistently, and update the search before submission.

Organising the literature:

Folders or tags in a reference manager.
A literature matrix with columns for author and year, setting, design and n, intervention, outcome, result, limitations and theme.
Arrangement by theme, by chronology, by study design or level of evidence, or by outcome.
Notes on each paper.

Classification of research designs (details in Study designs):

Group	Designs	Example question
Descriptive observational	Case report, case series, cross-sectional survey	How common is anaemia in adolescent girls in a district?
Analytical observational	Case-control, cohort, analytical cross-sectional	Is tobacco chewing associated with oral cancer?
Experimental (interventional)	Randomised controlled trial, non-randomised trial, community trial	Does tranexamic acid reduce blood loss at caesarean section?
Secondary research	Systematic review, meta-analysis	What do all trials of tranexamic acid at caesarean show together?
Qualitative	In-depth interviews, focus groups	Why do patients stop treatment early?

Computers in scientific research (role of computer applications in research)

Ph.D. RM 2014, 2017, 2018, 2020

Stage	What the computer does	Examples
Literature search	Searches databases, links full text, sends alerts	PubMed, Cochrane Library, Google Scholar
Reference management	Stores references, removes duplicates, formats citations	Zotero, Mendeley, EndNote
Protocol	Sample size and randomisation lists	Sample size calculators
Data collection	Electronic case forms with range checks	REDCap, tablet-based forms
Data storage and cleaning	Coding, error checks, backups	Spreadsheets, databases
Analysis	Statistical tests and models	Statistical software (Choosing a test)
Presentation	Tables and graphs	Data presentation
Writing	Word processing, citation insertion, plagiarism check	Writing and referencing
Registration and publication	Trial registration, online submission, repositories	CTRI, journal portals, Shodhganga
Communication	Email, shared documents, video meetings	Multicentre coordination

Advantages: speed, accuracy in calculation, handling of large data sets, reproducible analysis, easy sharing.

Limitations: wrong data entered give wrong results, software may be used without understanding the method, data security and confidentiality must be protected, cost and training are needed, and the work depends on power and internet.

Applications of computers in medical practice

Ph.D. RM 2018

Records and administration: electronic health records, hospital information systems, registration, billing, bed management.
Diagnosis: laboratory information systems, auto-analysers, imaging (CT and MRI reconstruct images by computer), picture archiving and communication systems (PACS).
Clinical decision support: drug-interaction and allergy alerts, dose calculation, reminders for screening and vaccination.
Monitoring: intensive care monitors with alarms, infusion pumps.
Telemedicine: teleconsultation and remote reporting. In India, the Telemedicine Practice Guidelines were issued on 25 March 2020.
Pharmacy and stores: prescriptions, stock and expiry tracking.
Public health: disease surveillance, registries, programme data.
Education and research: e-learning, simulation, literature access, audit.
Patient communication: appointments, reports and reminders.

Precautions: confidentiality and consent, data backup, cyber security, validated software, and the clinician remains responsible for decisions.

Functions of a library

Ph.D. RM 2017

Acquisition of books, journals and electronic resources.
Organisation: classification, cataloguing, online public access catalogue.
Circulation: lending, reservation, return.
Reference and information service: answering queries, helping with searches.
Access to e-resources: subscriptions and consortia (for example ONOS for government institutions), remote access.
Current awareness service and selective dissemination of information on new publications.
Document delivery and inter-library loan.
User education: training in databases, reference managers and citation.
Preservation and institutional repository: theses, archives, submission to Shodhganga.
Research integrity support: plagiarism-check software.
Facilities: reading space, computers, internet.

Ranganathan's Five Laws of Library Science (1931): Books are for use. Every reader his book. Every book its reader. Save the time of the reader. The library is a growing organism.

The one thing to remember

Write down the databases, the search terms and the date, so that anyone can repeat your search.

PubMed counts were obtained through NCBI E-utilities on 14 September 2026 and will change as records are added. Numbers are written in the Indian system (1,09,228). The sensitivity and precision example uses made-up numbers for teaching.

Sources: Boole G. An Investigation of the Laws of Thought. London: Walton and Maberly; 1854. Ranganathan SR. The Five Laws of Library Science. 1931. Richardson WS, Wilson MC, Nishikawa J, Hayward RS. The well-built clinical question. ACP J Club 1995;123:A12–3 (PMID 7582737). Bachmann LM et al. Identifying diagnostic studies in MEDLINE: reducing the number needed to read. J Am Med Inform Assoc 2002;9:653–8 (doi:10.1197/jamia.m1124). Greenhalgh T, Peacock R. BMJ 2005;331:1064–5 (doi:10.1136/bmj.38636.593461.68). Harris PA et al. REDCap. J Biomed Inform 2009;42:377–81 (doi:10.1016/j.jbi.2008.08.010). Bramer WM et al. Syst Rev 2017;6:245 (doi:10.1186/s13643-017-0644-y). Gusenbauer M, Haddaway NR. Res Synth Methods 2020;11:181–217 (doi:10.1002/jrsm.1378). Page MJ et al. PRISMA 2020 statement. BMJ 2021;372:n71 (doi:10.1136/bmj.n71). Rethlefsen ML et al. PRISMA-S. Syst Rev 2021;10:39 (doi:10.1186/s13643-020-01542-z). Lefebvre C et al. Chapter 4: Searching for and selecting studies. Cochrane Handbook for Systematic Reviews of Interventions v6.5.1, 2025. World Medical Association. Declaration of Helsinki, October 2024. National Library of Medicine: About PubMed, About MEDLINE, MEDLINE History, MeSH introduction and tree structures, and PubMed User Guide (accessed September 2026). Google Scholar Help. Board of Governors in supersession of the Medical Council of India. Telemedicine Practice Guidelines, 25 March 2020. Press Information Bureau. One Nation One Subscription, 1 January 2025. CTRI, Shodhganga and WHO ICTRP websites (accessed September 2026).

Past papers

Every TNMGRMU question on literature search

Each one is answered in this chapter. Tap a sitting to open the university's own question paper.

×2Literature SearchPh.D. RM · Jul 2019 Ph.D. RM · Jan 2016
×2Computer application in researchPh.D. RM · Jan 2018 Ph.D. RM · Jul 2014
×1Sources of a literature reviewPh.D. RM · Jul 2025
×1How would you conduct the literature review and organize the retrieved literature in Research? Explain in detail the classification of Research design and its concepts with suitable examplesPh.D. RM · Jul 2024
×1Organising literaturesPh.D. RM · Jan 2023
×1Sources of literature reviewPh.D. RM · Jul 2023
×1Computer aided search of literaturePh.D. RM · Jul 2022
×1Importance of Literature SearchPh.D. RM · Aug 2021
×1Write in brief about the role of Computer Application in Scientific ResearchPh.D. RM · Dec 2020
×1What are the applications of computers in medical practice?Ph.D. RM · Jul 2018
×1Functions of LibraryPh.D. RM · Jan 2017
×1Computers in scientific researchPh.D. RM · Jan 2017
×1Review of LiteraturePh.D. RM · Jan 2015
×1Discuss computer aided search of literaturePh.D. RM · Jul 2013