Stats - EBM Levels, Questions, Searching and Grades Of Evidence Flashcards
What are the 7 levels of evidence in the traditional hierarchy system?
1 Systematic reviews and meta-analyses of RCTs with definitive results
2 RCTs with definitive results (confidence intervals that do not overlap the threshold clinically significant effect)
3 RCTs with non-definitive results (a point estimate that suggests a clinically significant effect but with confidence intervals overlapping the threshold for this effect)
4 cohort studies
5 case control
6 cross sectional studies
7 case reports
What are the 4 basic steps in Evidence Based Medicine?
1) develop a focused clinical question
2) search for the best evidence
3) critically appraise the evidence
4) apply the evidence and evaluate the outcome
In step 1, we should consider background and foreground questions. What do each of these mean?
Background questions are general questions about conditions, illnesses, syndromes and patterns of disease, and pathophysiology (e.g. what are the side effects of statin drugs?).
Foreground questions are more often about issues of care. They query specialised and distinct knowledge needed for specific and relevant clinical decision-making (e.g. does hand washing in healthcare workers reduce hospital acquired infection?)
When addressing foreground questions the components of the search question are generally defined using the PICO system.
What is PICO?
Patient (P) What is the patient group of interest?
Intervention (I) What is the intervention of interest?
Comparison (C) What is the comparison?
Outcome (O) What is the primary outcome?
In searching for evidence, we have primary and secondary research.
What do each of these mean?
Primary (aka empirical research) - sources that contain the original data and analysis from research studies. No outside evaluation or interpretation is provided (e.g. RCTs, cohort studies, case-control studies, case-series, and conference papers).
Secondary - sources that interpret and analyse primary sources. These sources are one or more steps removed from the event (e.g. evidenced based guidelines and textbooks, meta-analysis and systematic reviews).
What are filtered sources?
Filtered resources summarize and appraise evidence from several studies and included systematic reviews, critically appraised topics, evidence-based guidelines and point of care references.
What are unfiltered sources?
Unfiltered sources are large databases of articles that have not been pre-screened for quality. The searcher must filter out the results that do not meet their requirements using either specific vocabulary terms of pre-formulated searches or terms by the database.
When trying to answer foreground questions, it if often necessary to search the primary literature for original research articles. In behavioural health, these studies are found in a number of literature databases, including Medline (PubMed), PsycInfo, CINAHL and EMBASE.
This type of search can be quite a challenge. Besides needing to locate and master multiple sources, many of the articles included in these databases are not evidence-based. Special search strategies and techniques are needed to filter through the many references to find patient-centred, systematically researched studies.
Which database dates back to the late 1890s. It began with the simple acquisition, cataloguing, and indexing of the literature of the medical sciences?
In 1964 a computer-oriented bibliographic retrieval and publication system was created, called….?
It was launched online in 1971 (accessable worldwide in 90s) and called…?
NLM (National Library of Medicine)
MEDLARS (Medical Literature Analysis and Retrieval System)
MEDLINE
How is MEDLINE indexed?
What descriptors are added?
MEDLINE records are usually created from electronic metadata sent by journal publishers to the NLM. However, indexing is still manually added to article entries by staff at the NLM.
This indexing includes basic error checking and the allocation of MeSH (Medical Subject Headings) descriptors to each article based on its content (MeSH terms are descriptors developed by librarians to organize and categorize topics).
What is MeSH?
Medical Sub Headings AKA MeSH is the NLMs controlled vocabulary thesaurus that consists of sets of descriptive terms organised in a hierarchical structure that allow searching at various levels of specificity
How does PubMed compare to MEDLINE?
There is much confusion about the difference between MEDLINE and PubMed.
PubMed is actually a larger database run by the National Centre for Biotechnology information (NCBI) a sub-section of the NLM, of which MEDLINE is the largest component.
In addition to the Medline subset, PubMed also contains:
1) In progress records (those not yet indexed into Medline)
2) Older records
3) Records considered out the scope of Medline (e.g. general chemistry and non-life science)
What is the name of the large European database that overlaps with MEDLINE by approx 30-50%?
How does it compare with Medline?
Embase (Excerpta Medica database)
Compared with Medline, Embase provides a greater coverage of European and non-English language publications. It also covers a broader range of topics concerned with pharmaceuticals, psychiatry, toxicology, and alternative medicine.
