Absolute
Risk Reduction (ARR) is the difference in the event
rate between control group (CER) and treated group (EER): ARR
= CER - EER.
Case-control Study involves
identifying patients who have the outcome of interest (cases) and
control patients without the same outcome, and looking back to
see if they had the exposure of interest.
Case-series is a report on a series of patients
with an outcome of interest. No control group is involved.
CER Control Event Rate: see Event Rate.
Clinical Practice Guideline is a systematically
developed statement designed to assist practitioner and patient
make decisions about appropriate health care for specific clinical
circumstances.
Cohort Study involves identification
of two groups (cohorts) of patients, one which did receive the
exposure of interest, and one which did not, and following these
cohorts forward for the outcome of interest.
Cost-Benefit Analysis converts effects into
the same monetary terms as the costs and compares them.
Cost-Effectiveness Analysis converts effects
into health terms and describes the costs for some additional health
gain (e.g. cost per additional MI prevented).
Cost-Utility Analysis converts effects into
personal preferences (or utilities ) and describes
how much it costs for some additional quality gain (e.g. cost per
additional quality-adjusted life-year, or QUALY).
Crossover Study Design :
the administration of two or more experimental therapies one after
the other in a specified or random order to the same group of patients.
Cross-Sectional Study the
observation of a defined population at a single point in time or
time interval. Exposure and outcome are determined simultaneously.
Decision Analysis is the application of explicit,
quantitative methods to analyse decisions under conditions of uncertainty.
Ecological Survery : based on aggregated data
for some population as it exists at some point or points in time;
to investigate the relationship of an exposure to a known or presumed
risk factor for a specified outcome.
EER Experimental Event Rate: see Event Rate.
Event Rate is the proportion of patients in
a group in whom an the event is observed. Thus, if out of 100 patients,
the event is observed in 27, the event rate is 0.27. Control Event
Rate (CER) and Experiemental Event Rate (EER) are used to refer
to this in control and experimental groups of patients respectively.
Evidence-Based Health Care extends the application
of the principles of Evidence-Based Medicine (see below) to all
professions associated with health care, including purchasing and
management.
Evidence-Based Medicine is the conscientious,
explicit and judicious use of current best evidence in making decisions
about the care of individual patients. The practice of evidence-based
medicine means integrating individual clinical expertise wi th
the best available external clinical evidence from systematic research.
Likelihood Ratio is the likelihood that a given
test result would be expected in a patient with the target disorder
compared to the likelihood that the same result would be expected
in a patient without that disorder.
Meta-analysis is an overview which uses quantitative
methods to summarise the results.
N-of-1 Trials The patient
undergoes pairs of treatment periods organised so that one period
involves the use of the epxerimental treatment and one period involves
the use of an alternate or placebo therapy. The patients and physician
are blinded, if possible, and outcomes are monitored. Treatment
periods are replicated until the clinician and patient are convinced
htat the treatments are definitely different or definitely not
different.
Negative Predictive Value (-PV) is the proportion
of people with a negative test who are free of disease.
Number Needed
to Treat (NNT) is
the number of patients who need to be treated to prevent one bad
outcome. It is the inverse of the ARR:
NNT = 1/ARR.
Odds are a ratio of nonevents
to events. If the event rate for a disease is 0.1 (10 per cent),
its nonevent rate is 0.9 and therefore its odds are 9:1. Note that
this is not the same expression as the inverse of event rate.
Odds Ratio describes
the odds of an experimental patient suffering an adverse event
relative to a control patient. See also section on Odds Ratios.
Overview is a systematic review and summary
of the medical literature.
Positive Predictive Value (+PV) is the proportion
of people with a positive test who have disease.
Randomised Controlled Clinical Trial a
group of patients is randomised into an experimental group and
a control group. These groups are followed up for the variables
/ outcomes of interest.
Relative Risk Reduction (RRR) is the percent
reduction in events in the treated group event rate (EER) compared
to the control group event rate (CER):
RRR = (CER - EER) / CER * 100
Risk Ratio is the ratio of risk in the treated
group (EER) to the risk in the control group (CER): RR = EER/CER.
RR is used in randomised trials and cohort studies.
Sensitivity is the proportion
of people with disease who have a positive test.
SnNout when a sign/test has a high s e n sitivity,
a n egative result rules out the
diagnosis; e.g. the sensitivity of a history of ankle swelling
for diagnosing ascites is 92 per cent, therefore is a person does
not have a history of ankle swelling, it is highly unlikely that
the person has ascites.
Specificity is the porportion
of people free of a disease who have a negative test.
SpPin when a sign/test has a high sp ecificity,
a P ositive result rules in the
diagnosis; e.g. the specificity of fluid wave for diagnosing ascites
is 92 per cent. Therefore, if a person has a fluid wave, it is
highly likely t hat the person has ascites. |
