Hierarchy of Evidence PDF

Hierarchy of Evidence BAS 5158 Lecture 2 Prepared by Dr. Rami Elshazli Associate Professor of Biochemistry and Molecular Genetics  Dr. Rami Elshazli  Hiera...

Hierarchy of Evidence BAS 5158 Lecture 2 Prepared by Dr. Rami Elshazli Associate Professor of Biochemistry and Molecular Genetics  Dr. Rami Elshazli  Hierarchy of Evidence Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  The hierarchy of evidence is a core principle of EBM.  EBM hierarchies rank study types based on the strength and precision of their research methods.  The systematic reviews and meta-analyses are at the top of the pyramid, and the expert opinion and background information are at the bottom.  The study with the highest level of evidence,  Observational studies and the lowest level i.e., systematic review or meta-analysis is at the evidence being case reports, case-series, or top of the pyramid, followed by randomized expert opinions residing at the bottom of the controlled trials (RCTs). pyramid.  Dr. Rami Elshazli  Hierarchy of Evidence Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  When searching for information, there seems to be different levels of credibility given to different types of scientific results.  Experts decided to rank this evidence to help identifying the best sources of information.  The criteria for ranking evidence is based on the design, methodology, validity and applicability of the different types of studies.  The outcome is called “levels of evidence” or  There are five levels of evidence in the hierarchy “levels of evidence hierarchy”. of evidence – being 1 for strong and high-quality evidence and 5 for evidence with effectiveness not established.  Dr. Rami Elshazli  Hierarchy of Evidence Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Level 1: (higher quality of evidence):  Level 4: (Case series):  Testing of previously developed diagnostic  Poor reference standard; analyses with no criteria on consecutive patients; values obtained sensitivity analyses. from many studies with multiway sensitivity analyses; systematic review of RCTs.  Level 5: (lower quality of evidence):  Expert opinion.  Level 2: Lesser quality RCT):  Prospective comparative study; retrospective study; untreated controls from an RCT; lesser quality prospective study; development of diagnostic criteria on consecutive patients.  Level 3: (Case-control study):  Retrospective comparative study; study of nonconsecutive patients without consistently applied reference “gold” standard.  Dr. Rami Elshazli  Types of Study Designs Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Case-Control Study:  A group of patients with a particular disease or disorder, such as myocardial infarction, is compared with a control group of persons who have not had that medical problem.  The two groups, matched for age, sex, and other personal data, are examined to determine which possible factor (e.g., cigarette smoking, coffee drinking) may account for the increased disease incidence in the case group.  Dr. Rami Elshazli  Types of Study Designs Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Case-Control Study:  Case Control Study is a study in which patients who already have a specific condition or outcome are compared with people who do not.  Researchers look back in time (retrospective) to identify possible exposures.  They often rely on medical records and patient recall for data collection.  Individuals split by disease.  Dr. Rami Elshazli  Types of Study Designs Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Case Report:  In medicine, a case report is a detailed report of the symptoms, signs, diagnosis, treatment, and follow-up of an individual patient.  Case reports may contain a demographic profile of the patient but usually describe an unusual or novel occurrence.  Case Series:  Case Series are descriptive study that consist of collections of reports on the treatment of individual patients.  Dr. Rami Elshazli  Types of Study Designs Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Cohort Report:  Analytical study in which a group having one or more similar characteristics (such as habit of smoking or a particular disease) is closely monitored over time simultaneously with another group (whose member do not smoke or are free from the disease).  Cohort Study is a study of a group of individuals, some of whom are exposed to a variable of interest (e.g., drug or environmental exposure), in which participants are followed up over time to determine who develops the outcome of interest and whether the outcome is associated with the exposure.  Dr. Rami Elshazli  Types of Study Designs Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Randomized Controlled Trial:  RCT is a prospective, analytical, experimental study using primary data generated in the clinical environment.  Individuals similar at the beginning are randomly allocated to two or more groups (treatment and control) then followed to determine the outcome of the intervention.  An experimental design used for testing the  In a single-blind study, only the participants are effectiveness of a new medication or a new blinded. therapeutic procedure.  In a double-blind study, both participants and  Individuals are assigned randomly to a treatment experimenters are blinded. group (experimental therapy) and a control group  In a triple-blind study, the assignment is hidden not (placebo or standard therapy). only from participants and experimenters, but also  The outcomes are compared. from the researchers analyzing the data.  Dr. Rami Elshazli  Types of Study Designs Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Systematic Reviews:  Systematic Review usually focuses on a specific clinical question and conducts an extensive literature search to identify studies with sound methodology.  The studies are reviewed, assessed, and the results summarized according to pre-determined criteria of the review question.  The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement, published in 2009, was designed to help systematic reviewers transparently report why the review was done, what the authors did, and what they found.  The PRISMA 2020 statement replaces the 2009 statement.  Dr. Rami Elshazli  Types of Study Designs Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  Meta-analysis study:  Following a systematic review, data from individual studies may be united quantitatively and reanalyzed using established statistical methods.  This technique is called a meta-analysis.  The justification for a meta-analysis is that, by combining the samples of the individual studies, the overall sample size is increased, thereby improving the statistical power of the analysis as well as the precision of the estimates of treatment effects.  Dr. Rami Elshazli  The PICO Framework Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt  The concept of PICO was introduced in 1995 to break down clinical questions into searchable keywords.  The PICO framework and its variations were developed to answer health-related questions.  PICO is a mnemonic formula originally developed to help investigators frame research questions when designing a study.  P stands for “Population or group of patients’ – have the  C stands for “Comparison” – did the investigators include investigators defined which population or patient group they a control group? If so, what was the intervention being are working with? P can also refer to the problem being given to the control group? investigated, for example, asthma in children.  O stands for “Outcome/s” – what outcomes of interest did  I stands for “Intervention” – did the investigators clearly the investigators measure to assess the intervention’s describe the intervention being given to the intervention effectiveness, and how were these outcomes measured? group?  Dr. Rami Elshazli Associate Professor of Biochemistry and Molecular Genetics, Horus University - Egypt