Intro to Evidence Based Practice

Bayes’ theorem

1. start with a prior belief about something (A)

2. you get new information (B)

3. you update your belief accordingly (A given B)

evidence based practice

based on:

• research evidence

• clinical expertise

• patient values

traditional decision making process

• experience and judgment

• patient preferences

• clinical circumstances

evidence based decisions

• experience and judgement

• patient preferences

• clinical circumstances

• + scientific evidence

theory

justifications for treatment based on basic or applied work designed to answer the question why something should work

evidence

justifications for treatment based on applied work (patients) designed to answer the question if something works

what does a practitioner need most: theory or evidence

evidence

level 1a and 1b

1a = systematic review of RCT’s

1 b = individual RCT

level 2a and 2b

2a = SR of cohort studies

2b = individual cohort study

level 3a and 3b

3a = SR of case-control studies

3b = individual case-control

level 4

case series, cross-sectional studies

level 5

expert opinion

RCT

= randomized control trial

• a study in which people are allocated at random to receive one of several clinical interventions

• one of the intervention is the control

advantages of RCT

• good randomization gets rid of bias

• blinding/masking to minimize bias

• results can be analyzed with statistical tools

• populations re clearly identified

• internal validity is stronger

internal validity

the extent to which a study accurately estimates the casual effect of an intervention within the study population

disadvantages of RCT

• expensive - time and money

• volunteer biases: may not be representative of whole population

• loss to follow-up

• can lack external validity

external validity

study findings cannot be generalized to other patients, clinicians, settings, or real-world conditions

cohort study

one or more samples (cohorts) are followed and subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial participants exposure characteristics are associated with it

retrospective cohort study

you already have the data, analyzing it

prospective cohort study

following them over time to predict

cohort study advantage

• subjects in cohorts can be matched, which limits confounding variables

• well-defined intervention, criteria, outcome is possible

• easier and cheaper than RCT

• external validity is stronger than RCT

• longer follow up period than RCT

cohort study disadvantage

• cohorts can be difficult to identify, match

• no randomization

• could take lots of time

• weaker internal validity… more bias to account for

case control study

compares patients who have a disease or outcome of interest with patients who do not have the disease or outcome → looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group

what type of study are case control studies

observational because no intervention is assigned

case control studies advantages

• good for studying rare conditions

• less time needed to conduct the study because the condition has already occurred

• simultaneously look at multiple risk factors

• useful as initial studies to establish association

• can answer questions that could not be answered

case control studies disadvantages

• some may have problems with data quality because they rely on memory and people will be more motivated to recall risk factors (recall bias)

• not good for evaluating diagnostic tests

• difficult to find a suitable control group representative of the target population

cross-sectional study

observational research method where researchers analyze data from a population at a single, specific point in time

• “snapshot” → comparing different groups

case report

describes and interprets an individual case, often written like a story

what do case reports often describe

• unique cases that cannot be explained by known diseases or syndromes

• cases that show an important variation of a disease or condition

• cases that show unexpected events that may yield new or useful information

• cases in which one patient has two or more unexpected diseases or disorders

why are case reports considered one of the lowest levels of evidence

they provide limited evidence for cause and effect

systematic review

a document often written by a panel that provides a comprehensive review of all relevant studies on a particular clinical or health-related topic/question

• created after reviewing and combining info from published and unpublished studies → summarize findings

systematic review advantages

• exhaustive review of current literature

• less costly than to create a new study

• less time required than a new study

• results can be generalized more broadly than individual studies

• more reliable and accurate than individual studies

• considered evidence-based

systematic review disadvantages

• very time-consuming

• may not be easy to combine studies due to lack of/inconsistent reporting

meta analysis

subset of systematic reviews but goes further → combines qualitative and quantitative study data from several selected studies to develop a single conclusion that has greater statistical power

meta-analysis advantages

• greater statistical power

• confirmatory data analysis

• greater ability to extrapolate to general population affected

• considered an evidence-based resource

meta-analysis disadvantages

• difficult and time consuming to identify appropriate studies

• not all studies provide adequate data for inclusion and analysis

• could required advanced statistical techniques

• heterogeneity of study populations can be challenging to account for

practice guidelines

aka “evidence-based guidelines” and “clinical guidelines”

• statement produced by a panel of experts that outlines current best practice to inform health care professionals and patients in making clinical decisions

practice guideline advantages

• created by panels of experts

• based on professional published literature

• practical guidance for clinicians

• considered an evidence-based resource

practice guideline disadvantages

• slow to change or be updated

• not always available, especially for controversial topics

• expensive and time-consuming to produce

• recommendations might be affected by the type of organization creating the guideline

steps in EBP process

1. identify need for info and develop a question

2. conduct a search for best possible evidence

3. critically appraise the evidence

4. integrate the evidence with clinical expertise and patient values

5. evaluate the effectiveness and efficacy of your efforts

background questions

• general knowledge about disease or intervention

• foundational knowledge about clinical condition

• reflect a desire to understand the nature of an individual’s desire or need

foreground questions

• helps you obtain specific knowledge

• assist in developing diagnosis, prognosis, or plan of care for a specific patient

PICO: defining the question

1. P = patient (or problem)

2. I = intervention (or cause, prognosis)

3. C = comparison (or control)

4. O = outcome(s)