 hello everyone in this video we are going to discuss about the various types of study designs in research and hence we can select the study design and also name the study design correctly before going to the presentation let me convince why study design is needed conventionally studies are designed based on the objectives and the available resource basically the choice of the study design is a tug of war between your objective and the available resources so at the end of the tug of war between the objectives and the available resources we agree with the particular study design and decide on the particular study design for our research even though they select the right study design many times researchers will not name it correctly so this presentation will help you to select the study design correctly and also to name the study design correctly the second important point why we need study design is that different types of analysis are needed for different study designs and also there are different guidelines for different study design especially the reporting guidelines the ethics all are different for different study designs and finally there are thousands of ways to do a study wrong but only a handful of ways to do a study properly so we have to remember this we can do it wrongly in many ways but we can do it correctly in only few ways now in health research the focus of our health research will be divided into these three concepts broadly divided into these three concepts that is either we will be looking at the risk factor of a particular disease or we will be looking at the diagnosis of a disease or we will be looking at the effectiveness of a treatment or an intervention so basically risk factors look at the cost quality of the disease how why the disease has been caused disease or the diagnosis test basically attempts to confirm the diagnosis of various diseases through various questions questionnaires clinical examinations radiological examination biochemical examinations etc etc then treatment aspect shows the effectiveness of different interventions either pharmacological non-pharmacological surgical medical all interventions comes under this classification this diagnostic test studies will be otherwise called as diagnostic study or variational studies basically we will be looking at accuracy parameters measuring at sensitivity specificity positive predictive values negative predictive values and also likelihood ratios will be there ROC curves those aspects will be covered in this diagnostic test but when we look at the cost quality that is at the risk factors and the effect of interventions we have this study design algorithm that is we need to ask one single question whether the investigator assign any exposure or intervention if yes then it will be an experimental study then we need to ask the second question whether we are doing random allocation for the study participants to get involved in different groups if yes that is the study participants are allocated on the basis of randomization into different groups then it is a randomized controlled trial if there is no random allocation for the participants to move into different groups then it will be called as non-randomized trials on the other hand if the investigator does not assign any intervention or exposure then it is called as a simple observational study under which the second question is if you have an comparison group then it is called as an analytical study if you don't have an comparison group then it is called as descriptive study simply descriptive study all your case series case studies comes under this descriptive study then if it is an analytical study you need to ask the third question the direction of the approach whether you are going from exposure to outcome or outcome to exposure if you are going from exposure to outcome if you are following up the exposure and looking at the outcome then it is called as a cohort study on the other hand if you start from outcome that is you start from the case back and measure the exposure it is called as case control study otherwise called as retrospective study on the other hand if you measure this exposure and outcome at the same time then it is called as cross sectional study or otherwise prevalent studies i'm having one one slide for all these study designs i'm going to explain this in coming slides before going to the individual slides let me explain about the hierarchy of the clinical evidence this is otherwise called as the evidence pyramid that is when we generate evidence for a risk factor or an effectiveness of an intervention then we have this is a evidence pyramid we have case reports opinions expert opinions commentaries all comes under the base of the pyramid and all these are will be observational studies at this level we have this descriptive study also here we generate the hypothesis above which we just try to confirm the hypothesis that is case control studies and cohort studies till here we don't give any intervention if we start giving intervention it becomes experimental studies we have quasi experimental studies and randomized controlled trials above which we have the studies of studies that is called as systematic review and meta analysis the tip of the evidence pyramid is dominated by this meta analysis down is the systematic reviews below which is the randomized controlled trial the base will be filled with the descriptive studies case reports case series editorials commentaries etc etc now first we will go to the case study or otherwise called as case report it is a detailed presentation of a single case which is either a rare presentation of a common disease or a common presentation of a rare disease not the presentation alone you can present a rare symptom or rare investigation picture then you can present it as a case study or case report we have a reporting guidelines for case report or case study that is commonly used is the CARE guidelines it stands for case report guidelines CARE CARE guidelines which includes the reporting checklist here are some of the case studies we have one severe vitamin B2L deficiency in pregnancy mimicking help syndrome rapid growth of pelvic cysts during pregnancy a case report mosaic turner syndrome presenting with the 46 XY aerotype all these are the examples of the case study or case report with single case described with the CARE guidelines we can use CARE guidelines to to write the better manuscript of a case reporter then we have case series when I say case report is a single case case series is a group of cases which may be ranging from 2 to 10 cases case series is an experience of a group of patients with similar diagnosis similar representations or similar picture of investigations or similar manifestations it is informative for very rare disease with very few established risk factors in case series basically we start the generation of the hypothesis the most common disadvantage with this case series is the selection bias we move on to the descriptive study as we say we don't assign any exposure or intervention and also we don't have a comparison group then it will be a descriptive study most of the hospital based studies in a specified population will come under this study design that is descriptive study descriptive study also generate the hypothesis it describes the disease in terms of time place and person time place and person epidemiologically but in case of hospital based studies we have other characteristics to express the disease or to describe the disease here is one example when few mothers with no antenatal care had low birth weight babies and described then it is a simple descriptive study it helps in the hypothesis generation one classical historical descriptive study john snow the father of epidemiology he identified the contaminated pump which gives water is responsible for the spread of the cholera through a descriptive study and he removed the handle and thereby he controlled the cholera effectively so this is the classical example of a descriptive study again we have cross sectional studies as we mentioned earlier under the observational study when we have a comparison group exposure and disease are measured at the same time then it is a cross sectional study or a prevalent study this is the basic analytical study which starts the testing of the hypothesis which starts with the testing of the hypothesis the same example if low birth weight and antenatal care were studied simultaneously then it becomes a cross sectional study it is used to study conditions that are relatively frequent with longer duration cross sectional study that is both exposure and disease are measured at the same time we have strobe guidelines for reporting the manuscript next in line is the case control study as we told here we start with the disease that is case and go back to the exposures and non-dissist and measure the exposure that is healthy controls or matched controls look for the exposure in the same example the birth weight normal and low birth weight babies are measured with the exposure of antenatal care then we can call it as a case control study historically thalidomide tragedy is the important first case control study to come up with the earlier identification of the usage of thalidomide resulting in fetal malformations again we have strobe guidelines for this strobe is common for all observational studies we have strobe case control study specifically that checklist will help you in writing the manuscript of a case control study advantages of case control study is simple easy cheap fast it has very minimal ethical problems no attrition as in case of cohort study and for rare diseases this is the suitable study design next we move on to the cohort study we start from the exposure and non-exposed look for the presence of the disease with the same study we measure the antenatal care first the mothers who received adequate antenatal care and the mothers who received inadequate antenatal care were followed for birth weight then it becomes a cohort study the group of roman soldiers having similar characteristics were termed as cohorts from there the code name cohort study has derived next we move on to the non-randomized trials that is in case of an experimental study if the study participants are assigned into different groups without randomization then it is called as non-randomized trials historically the first ever non-randomized trial was conducted by james lind for identifying this curvy so it is basically helpful in identifying the effectiveness of new treatment in experimental study if we do randomization it is termed as randomized control trial it is also useful for effectiveness of new treatment randomization is the heart of the study randomization is the heart of the study that is it eliminates the selection bias also it takes care of the confounders between the two groups then we have blinding that is masking the participants from being aware of which intervention they are getting that is called as blinding we have single double and triple single is at the level of participants double at the level of participants and interviewers triple triple blinding involves participants observers and also people who do the analysis consort guidelines are consolidated standards of reporting trials statements is useful in reporting randomized control trials the problem with the randomized control trials they are complex attrition is common and hence attrition bias will be common it takes time and it is costly to conduct also next on the list is the studies of the studies that is meta analysis and systematic reviews basically this study design collect all the studies related to the topic and analyze and given output most of the times it will be rcts so what the authors do in systematic review and meta analysis is they search for the studies and they collect all the datas and after filtering out for the quality of the studies they combine data and they give a consolidated finding or result out of those available studies so that is the purpose of the systematic reviews and meta analysis the difference between the systematic review and meta analysis is it combines all the studies and give a particular result but in case of meta analysis it will derive at a particular number then it will become a meta analysis this is the forest plot used in meta analysis this expresses that the first rct conducted in 1972 on antenatal usage of steroids for fetal maturation was showing the negative results then only by 1991 it started showing positive results if the meta analysis was not available at those at that point of time it would have taken at least 10 to 20 years to prove the effectiveness of antenatal steroid therapy for maturation of the fetus before I conclude I touch upon this topic that is the usage of reporting guidelines in case of the study designs there are different checklist available based on the study design we can go to this equatornetwork.org wherein you can access various reporting guidelines based on the study design that is for example here randomized control trial we have concert guidelines and also if you go to the extensions you can download many other reporting guidelines or other assisting documents which you can use for randomized control trials will be available in this site so observational studies we have strobe systematic reviews we have prisma case report we have care qualitative studies we have srqr diagnostic studies we have stard and tripod here economic evaluations cheers guidelines animal preclinical studies arrive guidelines study protocols we have split guidelines like this there are various reporting guidelines available in this equator network site you can go and access their various reporting guidelines based on the study designs so to sum up if the investigator assign an exposure it is an experimental study if not it is an observational study if random allocation is followed it is a randomized control trial if not it is an non-randomized control trial under observational study if you have a comparison group it is an analytical study if not it is a descriptive study under analytical study if you start from exposure to outcome it is a cohort study and you start from outcome that is case to exposure it is called as case control study you study both exposure and outcome then it is called as a cross sectional study so we need to identify the study designs correctly in order to choose the best choice of study design in our research then to name the study design correctly and also to use this reporting guidelines correctly to make our manuscript better thanks for watching this video if you haven't subscribed to our channel please subscribe if you like this video please share it to your friends click on the like button thanks for watching this video