The document outlines the importance of literature reviews in biomedical research, highlighting their role in identifying existing knowledge gaps and guiding new research. It emphasizes systematic information retrieval methods, such as utilizing databases like PubMed, and employing indexing mechanisms for effective searches. Additionally, it discusses the measures of disease frequency, including definitions of prevalence and the concept of populations at risk.

1. Basic Course in Biomedical Research
TOPIC – LITRETURE REVIWE AND
MEASURES OF DISEASE FREQUENCY

2. LITRETURE REVIEW:
• Literature review will guide us about existing knowledge and
scope for further research.
• It is an important link between what is known and what is
not known.

3. IMPORTANCE OF LITERATURE REVIEW:
• Saves lot of time in your research work.
Eg: We can use existing standardized, regionalized questionnaire.
• Know the subject matter better.
• Suggest new research topics, questions & methods.
• By finding certain lacunae in the existing knowledge, which makes
you to carry out your new research.

4. Literature review
• Information seeking
- Scan the literature efficiently using manual or computerized
methods to identify a set of potentially useful articles and books.
-It may be a text book, manuscript, published article or conference
proceeding.
• Critical appraisal
-The ability to apply principles of analysis to identify those studies
which are unbiased and valid.

5. Literature review:
• Organize information
-Relate it to your research question.
• Synthesize results
- Summary of what is known and what isn't known.
• Identify lacunae
- As appears in the literature.
- E.g., not availability of quick and easy diagnostic tool for TB.
• Develop questions for further research.

6. Information retrieval:
• Identifying, within a large document collection, a subset of
documents whose content is most relevant to user’s need.
- From Database organization (database management)
- By Structure of query (user defined)

7. Database structure and management:
• Database
- All information about a scientific knowledge in this information era
is currently stored mostly in an electronized form.
- Even certain non-electronized form is also stored in term of books or
in terms of printed journals or conference proceedings.
- E.g., it may be e-library, or collection of citations.
• Indexing mechanism
- To collect required information by means of set of queries from the
database.
- Cover all the terms in the database
- Common and frequent terms
- Used as delimiters

8. Appropriate place to search:
• General information about your specific health related event or a disease.
- HON (Health On Net) certified websites. (Authorised & Reliable)
- Web Search Engines – Google
• Specific query on specific scientific databases
- PubMed / Google Scholar / Embase database etc
- You can retrieve the required article or the required manual script.
• Archived full text articles
- Free Open Access
- Directories of journals
- Fee Based – From Libraries

9. Pubmed (https://pubmed.ncbi.nlm.nih.gov/)
• PubMed, which comprises more than 25 million citations of
biomedical literature.
• This PubMed is maintained by National Center for Biotechnology
Information situated in US National Library for Medicine under
National Institute of Health.
• It has collection of abstracts and full text articles.
• Each abstract has a link out resource, where the full text article is
available. There are certain articles where you can freely access in
PubMed, through a portal called PMC (PubMed Central)

10. MeSH (Medical Subject Headings)
• It is the US - NLM controlled vocabulary thesaurus used for indexing
articles for PubMed.
- we can see as keywords under any abstract.
- If your keyword is in concordance MeSH, then your article has
higher chances of getting identified by a set of systematic query
mechanism.
- we can access the entire MeSH database in the left side of your
portal

11. Searching a database:
A. Boolean query: AND
- Lung AND infections
- It retrieves the result of those articles, which are
specific to lung and infections.
B. Boolean query: OR
- Lung OR Infections
- It gathers information about the entire items on
lung, entire items on infections and even the items
which is common that is lung and infections.

12. • C. Boolean query:
-Lung NOT Infections.
-It gathers information about lung except
infections.

13. Selecting studies for Literature review:
• Read and critique all those studies you have found in searching databases.
• Select those of good quality.
- 8Critical appraisal should be scholarly.
- Eg: this study is for particular population (western) only and not
generalised to other region (Indian).
- You will identify lacunae, existing gap, which you can try to fill up by doing
your new research.
• Compare methods, results, findings etc
• Tabulate info from each study & Compare
• It will help to organise & compare various studies with each other.

14. Writing a literature review:
• Introduction
- Purpose of review
- Organization of review
- Basis for ordering
- Most important to least
- Earliest to most recent
• Empirical literature
- Includes quality studies relevant to topic.
- Explain each study using paraphrasing rather than direct quotes.
- Scholarly, but brief, critique of study’s strengths and weaknesses.
• Summary
- Concise presentation of the research knowledge about a selected topic -
what is known and not known & lacunae of an existing literature..

15. Ethical Issues:
• Content from studies
- Presented honestly
- Not distorted. - taking only a part of result as such.
• Weaknesses of a study
- Should be addressed scholarly in a research point of view.
- Not necessary to be highly critical.
• Sources should be accurately documented.
- Vancouver style / Harvard style
- It has to be cited accordingly.

16. MEASURES OF DISEASE FREQUENCY

17. Population at risk:
• Portion of a population that is susceptible to a disease.
• Can be defined on the basis of demographic or environmental
factors.
 Examples:
*Population at risk of developing carcinoma of the cervix:
Female population
- Age > 30 and < 70 years
- Population at risk of hepatitis B
- Those individuals anti-HBc negative

18. Prevalence – (P)
• Definition: Prevalence is the number of existing cases (both old and
new) in a defined population at a specified point of time.
-
• Whenever your population at risk is very large and you have number
of cases were small, you will get a value P as 0.001. So, in order to
make into a round number you multiplied by 1000, 10000 or 100000
(10n ).
• In some studies the total population is used as an approximation if
data on population at risk is not available.
• Types: A. Point Prevalence B. Period Prevalence

19. • Point prevalence:
 number of cases at one point of time, in relation to defined
population
 P = C/N
• Period prevalence:
 Frequency of disease over some time
 PP= C+I/N
C = Number of observed cases at time ‘t’
N = Population size at time ‘t’
I = Number of incident cases that develop during the period