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Literature Review

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hi I am dr. ganeshkumar from ICM a school of public health nationalists of epidemiology this lesson is about literature review literature review is an important step in any health research because this is an important link between what is known and what is notknown basically research is an systematic investigative process toincrease our existing knowledge about your concerned subject of interest or to revise our existing knowledge so it maybe basic or applied where basic is increasing an existing knowledge where applied is that applying this basic research to develop new processes new products new knowledge or to throw a light of an unknown area in this context literature review is an important stepin any health research where it is going to tell us where it helps and answers to tell us to guide us what is already existing knowledge about a concerned subject so here in this session the most important learning objectives are why we require a literature review what is aliterature review how a literature review is performed and what are the steps of the literature review and certain ethical concerns in anhydrous review so why we require in a literature review as we already explained in the definition of a research that it is a important link between what is known and what is not known so for to know that we require this important step called literature review where it says lot of time in your research and second it know the subject matter better so this throws what is her existing knowledge about the concern subject and it suggests the new research topics and questions for example how it saves yourself from work when you see when you want to develop your questioner for a physical activityokay so we you review a literature you can come across an already existing standardized region analyze a questionnaire for physicalactivity so you can use that which you know need to spend lot of time to develop a new questionnaire to measure the physical activity of an individual and of course it paves a way and throws a light of to know the subject matter better and third by reading than existing articles you may find a certain lacunae in the existing knowledge which makes you to to carry out your new research so it will age you to carry out a new questions it is you to develop new research questions it heats you to develop new methods of an existing knownsubject so is it just a summary that so we are going to read whatever it is known and we are going to summarize it until then this is what it is there in the existing literature or existing evidence no it is not just a summary it is first step it is basically an information seeking so it scan the literature efficiently using manual or a computerized methods to identify a set of potentially useful articles say like how we usually do in literature reviews that the whatever the kind of aresources valid resources over an existing subject we need to retrievethat information from that so it may be a text book it may be a manuscript it may be a published article or it may be a conference proceeding so from that we need to go through that and we need toretrieve a kind of an information from that and second thing is that after we have collected all those things what we basically do is not just summarize it we need to critically apprise whatever the article we have collected so far so the critical appraisal is the most importantstep in in literature review which is an ability to apply principles of analysis to identify which is useful for you so these will be useful for me this will not be useful for me this is valid for this concerned subject this is not valid for my point of view so likewise you need to critically appraise an existing collected literature so this is not just a summary so the what it is done it is the organized research how organized it is so organize the research it's a systematic process so in that for say like the first important thing is that you need to organize the information what whatever you have collected so far and you have to relate it to the concerned research question which you are trying to develop a which you have already identifying it and second thing is that it helps a second step is that it synthesizes the results of it so from this existing whatever information which we have collected so in that collected information you have to summarize it what is and what it is not known so so this is all summarizing that is called synthesizing the results and third step is that you need to identify the lacunae when you synthesize the results when you organize a newsynthesize the results the third thing that you can see is that which is the lacunae here as appears in the literature that means it for example after when you are trying to review the existing diagnostic tools of tuberculosis and after you have reviewed that there are many tools are available and this is the different cost of the different diagnostic tools and these are the different or work easy friendlinessquicker the results and you can identify that there is no quicker tool which is not available for specific type of tuberculosis now though this gives a lacuna of the existing literature so this may be helping you and this will lead you to identify a new research question oridentifying a new research path in it so that's how it is an organized research it is not just summarizing this existing articles and writing a kind of a paragraph so if you so when you have seen that you can see there is an information retrieval mechanism is inculcated in the literature review so information literature information retrieval in literature review what it is it is basically identifying from a large database and from that by a set of queries you are going to identify what are the documents which is relevant for your needs so that is called information retrieval that it happens from here big databaseand it may be a huge database where all these articles are archived collected or whichever is stored into that and from that you user by means of a set of Curie is seeking an information from this databaseoh no this query system is user-defined it basically according to the need which a user is developing into that over the particular research question so what actually is this database and what actually this database management what is this a set of queries so you see hereall this information about a scientific knowledge in this information era is currently stored mostly in an electronic forms even certain non electron eyes the form is also stored in terms of books or in terms of printed journals or conference proceedings all these things are collectively called as a database for example maybe a year later re forexample it may be a collection of citations so this database is will behuge from this like a lost page of a book a textbook you can see index which helps you to identify what you are trying to search likewise there are certain indexing mechanism for these databasefrom value are going into collector required information by means of set of queries so that is called indexing you know this set of Curie is what user is defined to retrieve the required information from these huge databases okay so where we how to such which is the appropriate place to search the required information where we need to search it may be a general information about a specific health related event or a disease for this already we know that Google is a huge search engine which has a huge database of the requiredinformation in it but from all the Google results we know we cannot rely entirely on that so there is a kind of an accreditation mechanism by a nonprofit organization called health arnett so this is called heo and certified websites this hello and certified websites are those areaccredited websites where you can get certain means of an authorized certain means of and reliable information about a specific health-related even so that's how about a general information but by a professional by a researcher so what is specifically when you want to retrieve an information for example I need to retrieve an information about are all clinical trials about diagnostic tests on tuberculosis okay so when I am I'm going to do this kind of a specificquery this specific curry has to happen over as the specific scientific database which are PubMed which is a huge database of scientific science biomedical citations it will be a Scopus which is also a huge database or even Google Scholar is also on another URL which is an another portal where a huge collection of citations and abstractsacross the literature is available so from this a specific query you canretrieve the required article or the required manuscript which you are trying to search and third it may be from your archived full-text articles the archive the full test articles are usually available in free open access directories of journals or it may be from a fee-based libraries and this libraries may be a library or may be a physical library which is present where full-text articles are that from therewhere we can able to get the required information which we are Intendant to search over your concern to topic and finally you want to take the articles or you want to review those articles which is evidence-based which was the highest level of evidence currently available is the systematic review and meta-analysis so from this collection of systematic reviews and meta-analysis also you can retrieve that information and which is available in Cochrane Libraryand even certain databases also have this collection like map of Medicine is also a collection of evidence-based medicine articles in that portal so so these are the places where you can do a querysearch specifically by an indexing mechanism and the required information can be retrieved from these databases the most popular among all these things is permit so PubMed is a huge databasewhich has 25 million citations is available and another commonly used portal is Cochrane Library which is a collection of systematic reviews and meta-analysis okay so this popular pubmed let's see about it what is this permit so PubMed which has more thanwhich comprises more than 25 million citations of biomedical literature this PubMed is maintained by the National Center for Biotechnology information situated in US National Library for medicine under National Institute of Health and this permit is free and open to access and each and every permit it is a collection of abstracts and full-text articles each abstract has a link out resource where the full-text article is available and there are certain articles where you can freely access in PubMed through a portal called PMC which is called PubMed Central so Threepio through this PubMed Central portal you can see this free full-text articles about your concerned topic of interest or your research question and there is a good tutorial which is available in the landing page of the PubMed where you can see in the portal itself apart from that this USNational Library of Medicine is maintaining their own set of definedpredefined vocabulary called mesh which is called medical subject heading medical subject heading is a National Library of Medicine controlled vocabulary the Sarris which is you can see as Kyle as calledkeywords under any abstract if your keyword is in concordance with the NLM defined a vocabulary called mesh then your article has a higher chances of getting identified by a set of systematic query mechanism so that is why mesh terminologies are very important which you can access the entire mesh database in the left side ofyour portal a PubMed landing portal and when you see in the PubMed portal there you can have a tutorial which is available this entire tutorial explains to you that using PubMed how to make asearch in the PubMed how to make asearch through a mesh terminology and how to search through a single citation manager and how to search through then Arthur Year why is a search article wise search study design wise search so itaids you this entire tutorial which has you a quick tour video tutorial is also available in the landing portal and when you access it it learns it gives you a good detail the form of how to perform your research of to perform your search in PubMed portal okay now I will explaina basic search in your database how to do your basic searching in your database and this kind of search is called boolean query which is very common in any search engine may be weber's a search engine it may be Google or it may be MBS it may be a PubMed this boolean query is a standardized one it uses this most important connection is called and are not queries in this boolean gorilla-likei will just give a demonstration about how actually when you are putting a query and how the information is retrieved for example here I am showing you two different database one database is about lung another database is about infections which encompasses allinfections and if I am putting a query a boolean query of lung and infections and how the Curie retrieved the result itretrieves the result of lung and infection which is those articles thoseitems which are specific to lung and infections okay whereas when I am putting a query about lung or infections what it gathers is it gathers a information about the entire items on lung entire items on infections and even the items which is common that is lung and infection which is lung infections so we get a huge search of results when you are putting a query called lung Orion functions when you put a curry called lung not in functions so in this lung not in functions what actually it totally removes this entire informationrelated to infections from the whole search again the infections related articles and items from the lung so what do you get is the results are the items which is related to all items which is related to lung except in functions so so this is how this boolean query worksand are not I will give a basic demonstration similar to that how I dida boolean query in PubMed so here you can see these are all the screenshots which I have cropped when you see when I made a boolean query of only lung what are the dotty enough total number of items which I have retrieved the total number of items have you retrieved is nearly 7.2 lakh only in functions the total number of items which I have resulted is 17.7 lakh when they put a Berlin query of lung and in functions so it resulted me one day eighty twothousand through eighty-two thousand articles are related to only lung Undine functions so it removes all other lung related all other infection related and it resulted specifically to lung and infunctions so let say this gives another screenshot when I make a search of boolean query of lung or infections here you can see where we get information of entire information on lung all the items about infections and all the items related to lung on infections so totalis that nearly 24 so that is how depends upon your billion query say like lung not infections in lung not infections it removed all thein functions related items and resulted one Li say like nearly six point three lakh which is only articles related to lung except in functions so this a small demonstration which gives you the an idea about how a boolean query works however this is not a structured a systematic way how to do here PubMed search and this session is not going tocover entirely how to do a mesh search and all so those tutorials are already available in the PubMed comm landing page so this is how a boolean query works in any search engine including table but now what are the steps how we have to do your literature review already we know that after we have organized the information is that whichare the study sources related to you that how we are selecting the studies the step one is that by means of yourboolean query or by a structured query system you are collected you are specific articles related to the for example you are searching a boolean query of same long-running functions I want one Lee RCTs about lung and instructions which is published in the past five years now I have organized everything so what you need to do is that after you have organized it you need to read all those articles andcritically a price elite and how to do this will be explaining you at thesecond step okay the second step is that you have to select which is of those with good quality remember here this critical appraisal should be scholarly it should not be too critical it should be scholarly for example an article is explaining about the randomized controlled trial about a therapeutic regimen over lung infections and whichyou have seen is that these are CTS whichever you have collected isaddressing over only the Western population and you have this lacunae so what you are going to critically appraisal is that the existing evidence is available over the Western population an Asian population is not available an Indian population is not available andthose articles whichever is reported about Indian populations are only quasi experimental studies here it is scholarly critically appraisal you are not too critical you are not finding your fault on it so when you do a scholarly critical appraisal on it you will identify your new area of research you will identify what is the existing lacunae existing gap which you can try to fill up by doing your new research third step is that you need to compare the methods results findings of allthose articles which you have organized it so when you compare it you can understand what is the existing knowledge about the different methodologies they have conducted in this particular topic so that gives you that throws you a light more about what is the methodology they have followed so far in those kind of an article and of your search query for example here when you want to do a therapeutic regiments on lung infections so here this what are all the methodologies they have applied well they want to test a therapeuticregimen for any lung infection so likewise okay and final step is thatyou need to tabulate in your form each study it has to be tabulated when you tabulate it it helps you to organize number two it helps you to compare number three it helps you to compare theindividual studies by itself and under itself with other studies and it will give you a good idea about and it will helps you to critically appraise on it this is how a model table looks like this an example table of literature where you can see you can put up add and delete your required columns I made an example table you can see citationdesign objective study population sample size what are the measurable outcomes what are the main findings and what are the author's conclusions you can organize it in kind of your table whichgives you helps you to critically appraise it and it is better even youorganize this table chronologically which is from recent to past so your recent studies can be tabled can be made in the first initial rows it helps you to select those recent evidences are reason existing knowledge about it so after you have organized all these things you have tabulated it now you need to write this literature review inthe literature review in the right apart these are other three important parts the first part is introduction when you are writing a literature review in the introduction it gives you that what is the purpose of the review why you are doing this and how you have organized this review or initiation of the review how you made the queries and how you have collected this information and how you have organized it and that explains and basis of the ordering most important to listen as well as what is the earliest to recent or recent to the alias' how you have organized it it gives you an introduction how you have written how you did this literature review and second is that where you are actually writing all your existing information empirical literature so it includes so the quality studies which isrelevant to your research question or the topic and it explains each study about its positive and in your fair addressing manner and your critical appraisal should be scholarly way so that explaining it or that these are all identified laocoön ease and these are all the strengths these are the novel methods so this you need to write in this part okay and finally you need to summarize you are existing this entireliterature review and you summarize it it should be a concise to be where you are going to tell that this is about their existing knowledge about your research question or a concern topic andthis is not known and this is not known and this is a lacuna of an existing literature so this is how you how to end a literature review write-up and there are certain ethical issues which we need to concern when you are doing a literature review mostly this problem is that when you are retrieving an information from your specificmanuscript or an article the content from the study should be present at honnest it should not be distorted thatyou should not be read in between lines and taking only a part of a result as such that's the most important thing so againis that any weakness of the study again I've been emphasizing it that it should be very scholarly it should not be too critical and it has to be addressed in an research point of view that's a scholarly point of view and finally yeah the source should be accurately documented so there is a way how a soul should be documented there are differentstyles are available very popularly followed Silas a Vancouver still even Harvard style is available and based on that it has to be cited accordingly those sources so finally this is how a literature review can be done and this gives you a basic view about what is a literature review why this literature review has to be done what are the stepsin doing this literature review and how you can write a literature review. Thank you very much