00:00
So let's talk about now some of the studies
that you might find and in another lecture
we're going to go further in detail into the
qualities of these studies and why some might
be more causal or of higher quality than others.
The first is the RCT, or the randomized controlled
trial. This is when you've got a group of
patients that been randomly allocated into
two groups; one group received the treatment
and the other group receives a placebo or
control. This is considered to be the gold
standard of evidence, because we can reliably
test for causal relationships. Did this treatment
cause that outcome? We would like to find
RCTs, RCTs make us excited. The next two studies
are going to be cohort and case-control studies.
00:47
These are what we call observational studies,
we don't interfere in the variables of observational
study, instead we watch them unfold in the
universe naturally. The first observational
study is the cohort design, that's when we
find some people who've been exposed to something
of interest, some other people who haven't
been exposed and we look forward in time to
see the proportions in each of those groups
that determine an outcome. Similarly a case
control is also an observational study, but
it's backwards, it's the opposite of a cohort
study. That's when we ascertain which patients
have the outcome we care about, those are
the cases, we find some other patients who
don't have that outcome, those are the controls,
we look back in time to see who had the exposures
of interest and again, we're going to go in
greater detail into these designs in a future
lecture. Case series are a poor quality of
evidence, they are descriptions of individual
patients and very often there is no control
group involved. A case report is one instance,
several reports make up a case series. Systematic
reviews on the other hand, are considered
to be very good evidence depending upon the
studies that are included in them. A systematic
review is a summary of literature of several
studies that have been brought together to
answer a larger question. Related to systematic
review is a meta-analysis and some people
confuse the two, some people will use the
term meta-analysis and systematic review interchangeably,
but they are distinct concepts and meta-analysis
is when we take the summaries or the estimates
from a variety of studies and mathematically
synergize them all, if that's a word, we make
one estimate from all of them, mathematically.
02:33
A systematic review doesn't necessarily do
that, so a systematic review can include a
meta-analysis, but it doesn't have to. So
those are the six basic large categories of
study types that we will find in our search,
again the RCT is the gold standard, a systematic
review of RCTs might even be better.
02:59
So what do we do with all this information
now? We're going to use our well phrased research
question to search for evidence, to search
for which studies are relevant to the question
that we care about and we're going to apply
what's called the pyramid of evidence to determine
which studies we should perhaps give more
weight to because they're probably better.