Evidence Rating
The evidence for ASERNIP-S systematic reviews is classified as Good, Average or
Poor, based on the quality and availability of this evidence. High quality evidence is
defined here as having a low risk of bias and no other significant flaws. While high
quality randomised controlled trials are regarded as the best kind of evidence for
comparing interventions, it may not be practical or ethical to undertake them for
some surgical procedures, or the relevant randomised controlled trials may not yet
have been carried out. This means that it may not be possible for the evidence on
some procedures to be classified as good.
Good
Most of the evidence is from a high quality systematic review of all relevant
randomised trials or from at least one high quality randomised controlled trial of
sufficient power. The component studies should show consistent results, the
differences between the interventions being compared should be large enough to be
important, and the results should be precise with minimal uncertainty.
Average
Most of the evidence is from high quality quasi-randomised controlled trials, or from
non-randomised comparative studies without significant flaws, such as large losses to
follow-up and obvious baseline differences between the comparison groups. There is
a greater risk of bias, confounding and chance relationships compared to high-quality
randomised controlled trials, but there is still a moderate probability that the
relationships are causal.
An inconclusive systematic review based on small randomised controlled trials that
lack the power to detect a difference between interventions and randomized
controlled trials of moderate or uncertain quality may attract a rating of average.
Poor
Most of the evidence is from case series, or studies of the above designs with
significant flaws or a high risk of bias. A poor rating may also be given if there