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EBHC definitions

Evidence Based Health Care Definitions

QuestionAnswer
CONSORT statement "Consolidated Standards of Reporting Trials"; a checklist of info that should be included in publications of clinical trials; adopted by many medical journals; allows for standardization;
which section of an RCT requires the most critique, as it could contain a fatal flaw, invalidating the results? Method's
Null hypothesis statement of no difference
Describe the 3 members of an IRB (investigational review board) 1- representatives from various health disciplines; 2- specialists in a nonscientific area (law/ethics); 3- Lay person not affiliated w/institution (most important);
Stratification a sophisticated randomization procedure designed to achieve similarities in known and unknown baseline patient characteristics between the groups;
single blinded patient or researcher is blinded (doesn't know who's got rx vs placebo)
Double blinded both patient and researcher are blinded
Triple blinded patient, researcher, and 3rd group (ex- radiologists interpreting results) are all blinded;
Double-Dummy a term used when more than 1 placebo is needed to perform blinding;
when is blinding the most important the more subjective the end point, the more important blinding is.
Placebo-controlled trials When placebo is used to determine efficacy of a drug compared to the natural course of disease; often used to get a drug FDA-approved;
Active-controlled trials determine the efficacy of a drug compared to another drug; used when it is unethical to do nothing, or when comparative efficacy is desired;
Noninferiority Design shows that a difference between 2 drugs is small enough to conclude that the test drug has an effect not too much smaller than the active control. Design used when superiority is not anticipated; design and interpretation are different from normal RCT's;
Parallel design when group 1 gets the actual drug until the trial end, while group two gets the placebo until the trial end;
Cross-over design when group 1 and two both get the drug and placebo during a trial, but at different times;
Advantage of cross-over design each patient serves as his/her own control; won't have a table of baseline characteristics; eliminates concern of complete randomization, but introduces a new obstacle of timing, and therefore can't be used with diseases that get better/worse with time;
Placebo Run-in a period of time inwhich all patients receive a placebo before the active vs placebo phase begins; helps to screen out placebo-reactors (benefit from placebo alone) and non-compliant patients;
Washout period period of time during which no drug for the disease to be evaluated is given; used at the start of any trial or in the middle of a cross-over trial; gets rid of other drugs that may be in the system;
Surrogate Markers laboratory measurements or physical signs that directly measure how a patient feels, functions, or survives; ex- cholesterol, HbA1c; Changes are expected to reflect changes in clinically significant endpoints;
Composite endpoint a clinically meaningful endpoint that includes more than 1 event; it's usually the primary endpoint of event driven trials; used because individual events occur in small numbers;
Power ability to accurately detect differences between groups; describes if the sample size was large enough to detect small differences; should be done prior, but can be done after the study; anticipate dropouts; = 1-beta;
alpha the probability of a false positive; typically set at 5%;
Beta probability of a false negative; typically set at 20%; = 1-power;
Delta the amount of difference in order to be statistically significant; variable, and dependent on the primary endpoint; the smaller the delta, the larger the sample size needed;
false positive finding a statistically significant difference that is not due to the drug, but due to chance; equal to alpha (5%);
false negative finding a real difference that is not statistically significant, due to chance or small sample size; probability is equal to beta (20%)
P-value indicates whether a difference is statistically significant; determined by alpha; P should be less than alpha;
Meaning of P-vallue < alpha statistic is significant, and not due to chance (true difference);
Meaning of P > alpha statistic is not significant; due to chance;
Intention to treat analysis Analysis of all subjects in a trial regardless of whether they completed it or not; estimates effectiveness (how drug works in the real world)
Per Protocal analysis analysis of only patients who complete the entire trial; estimates Efficacy (how drug works under controlled conditions)
Modified intention to treat an intention to treat analysis that is modified however described, but comonly "involving all patients with at least 1 post-baseline measurement"
nominal data catagorical data; ex- MI, death, etc
Ordinal data data that is on an arbitrary scale that reflects ranking; ex- pain scale, or new york heart association classes for HF;
Continuous (interval or ratio) data that is on a scale in which measurements have an equal distance between points; ex- Blood pressure, cholesterol, weight;
When to use parametric tests when the endpoint is normally distributed (bell shaped)
When to use nonparametric tests when the data is not normally distributed (not bell shaped)
When does the distribution (bell curve) apply? When the data is continuous
one tailed test used when the direction of the relationship is known.
two tailed test used when the direction of the relationship between variables is not known; requires a stronger relationship to acheive statistical significance (preferred method);
survival analysis analysis for nominal endpoints that may occur at any point in time; different because time prior to event is considered (ex- survival time); patients who drop out or who don't experience are "censored";
Kaplan-Meier curve a survival analysis that presents as a graph of cumulative survival over the trial period;
Log-rank test most common statistical test for "survival time" and "2 independent groups"
Central tendencies a way of reporting data/results including: mean, median, mode;
Mean the average of a data set
Median the mid point of a data set
mode the most common data point
Range a type of variability that describes the smallest to largest data points
interquartile range difference in scores at the 75th and percentiles; describes variability;
Standard deviation degree in which data points deviate from the mean; 68% describes 1 standard deviation;
Ways to evaluate nominal data (central tendency & variability) mode
Ways to evaluate ordinal data (central tendancy & variability) median, mode, range, interquartile range
Ways to evaluate continuous data (central tendancy & variability) mean, median, mode, range, interquartile range, standard deviation
Confidence interval a numerical range that contains the true value of the population a certain percentage of time; estimate of what would happen in the entire population; typically 95%;
Interpretation of confidence intervals when CI is crosses 0 or 1 (below or above), p-values are not statistically significant; when CI does not cross 0 or 1 (below or above), p values are statistically significant;
relative risk ratio of risk of an event occuring in one group compared to another group (usually placebo);
Interpretation of relative risk (RR) if RR < 1, drug decreases the risk of an event; If RR > 1, drug increases the risk of an event; If RR = 1, drug has no impact on the event;
Relative risk formula (RR) % of risk from the drug divided by the % of risk in the placebo population; want the number to be lower;
Hazard Ratio (HR) used in place of relative risk; used with survival data; want the number to be lower;
Odds Ratio (OR) used in place of relative risk; used in observational studies; want the number to be lower;
Absolute risk reduction (ARR) The percentage of patients who were spared the event because they received the drug;
Formula for absolute relative risk (ARR) % placebo that experienced the event - % drug that experienced the same event; want this number to be higher;
Relative risk reduction (RRR) the percentage of baseline risk that is removed as a result of the drug; percentage less likely that a group was to experience the event because they received the drug;
Formula for relative risk reduction (RRR) 1-RR x 100; want this number to be higher;
Number needed to treat (NNT) the number of patients who required treatment with the drug to prevent one event; time course must be included;
Formula for number to treat (NNT) 1/absolute risk reduction (ARR) as a decimal; ex- if ARR is 4%, (1/.04), NNT is 25 patients; want this number to be lower;
Created by: jonathanh21