.-
help for ^metannt^
.-
Estimates of absolute benefit or risk from meta-analysis
--------------------------------------------------------
^metannt , measure(^or|rr|rd^) size(^#^) confint(^#,#^) baseline(^#[,#...#]^)^
Description
-----------
This program is intended to aid interpretation of meta-analyses of binary
data by presenting the effect sizes in absolute terms. Both the number
needed to treat (NNT) and the number of events avoided (or added) per
1000 are presented.
The ^Number Needed to Treat (NNT)^ is the number of individuals required
to experience the intervention in order to expect there to be one
additional event to be observed. Assuming the event is undesireable, this
is termed the "number needed to treat to benefit" (NNTB). If the
intervention arm experiences more events, this is commonly refered to as
the "number needed to treat to harm" (NNTH).
^metannt^ calculates this by deriving an effect size (e.g. a risk ratio),
applying it to a population with a given event prevalance, and from this
deriving a projected event rate if the population were to receive the
intervention. The NNT is equal to
1/(control group event rate - treatment group event rate).
The ^number of avoided or excess events (respectively) per 1000 population^
is the difference between the two event rates multiplied by 1000. The
intervention group event rate is calculated in the same manner as with
the NNT. Optionally a confidence interval is also presented, using the
confidence limits of the effect size applied to the control group event
rate.
Options for ^metannt^
-------------------
^baseline()^ specifies the baseline (ie. control group) event rates, from
which the NNT and number of events avoided are computed from. More than
one baseline event rate may be specified.
^measure(^rr|or|rd^)^ specifies whether the estimated effect size pooled is
a risk ratio, odds ratio or (absolute) risk difference.
^size(^#^)^ denotes the size of the effect
^confint(^#,#^)^ denotes the confidence interval around the effect size.
By default the saved results from the r() macros within @metan@ are used to
derive the control group event rate, the effect measure, the effect size and
its confidence interval. However, unless a recent version of metan (1.71
onwards) was used immediately beforehand, the first three options must be
specified. The confidence interval is optional.
Examples
--------
. ^metannt , measure(rr) size(0.2) baseline(0.1,0.2,0.3)^
. ^metan tdeath tnodeath cdeath cnodeath, or^
. ^metannt , baseline(0.15)^
Authors
-------
Michael J Bradburn, Jonathan J Deeks, Douglas G Altman.
Centre for Statistics in Medicine, Institute of Health Sciences,
Old Road, Headington, Oxford OX3 7LF, UK.
email mike.bradburn@@cancer.org.uk
Also see
--------
On-line: help for @metan@ (if installed), @meta@ (if installed)