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help for ^epiconf^
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Assessing confounding effects in epidemiological studies
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^epiconf^ yvar xvar, [^con^(covlist) ^cat^(covlist) ^m^odel(string)
^nog^raph ^b^ackward ^e^xpos(varname) ^d^ead(varname) ^det^ail
^l^evel(#) ^co^ef graph_options]
^epiconf^ calculates the change in effect estimates such as odds ratio,
rate ratio, or hazard ratio after adjusting for a potential confounder
using either "forward selection" or "backward deletion" strategies.
^epiconf^ also calculates and graphs adjusted effect measures and
their confidence intervals. The order of variables being selected is
based on the "importance" (magnitude) of "change in estimate".
Variables required
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^yvar^ -- dependent variable, binary variable for logistic or poisson
regression; survival time variable for Cox proportional hazards
model.
^xvar^ -- exposure of interest
Options
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^con^ -- list of potential continuous confounding variables.
^cat^ -- list of potential categorical confouding variables.
^m^odel^(^string^)^ -- specifies the regression method, default is
logistic regression (^logit^), ^poisson^ and ^cox^ can be
specified.
^nog^graph -- suppresses graphs. By default, a graph is given.
^b^ackward -- specifies selection strategy as "back deletion method",
otherwise, "forward selection" method is default.
^e^xpos(varname) -- specifies a variable that reflects the amount of
exposure over which the ^yvar^ events were observed for each
observation. This is the option only for ^poisson^ regression.
^d^ead(varname) -- specifies the name of a variable recording 0 if
censored and nonzero -- typically 1 -- if failure. If dead() is
not specified, all observations are assumed to have failed. This
is the option only for ^cox^ regression.
^co^ef -- graphs regression coefficients instead of effect estimates
for graphs.
^det^ail -- gives details at each step. Default only gives a summary.
^l^evel(#) -- specifies the confidence level, in percent, for
calculation of confidence intervals (default=95%)
^graph_options^ -- some options with ^graph^ are allowed; see help
@graph@.
Examples
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. ^epiconf dead ab_uria, con(sbp weight) cat(sex agegroup)^
Calculates and graphs crude and adjusted odds ratios using
logistic regressions with a forward selection approach.
. ^epiconf dead ab_uria, con(weight sbp) cat(sex agegroup) m(poisson)^
^e(time) detail^
Calculates and graphs crude and adjusted rate ratios using poisson
regressions with a backward deletion method. Details in each step
are given.
. ^epiconf time ab_uria, con(age weight) cat(sex) m(cox) dead(dead) nograph^
Calculates crude and adjusted hazard ratio using Cox proportional
hazard models a backward deletion method, suppressing graph.
Author
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Zhiqiang Wang
Menzies School of Health Research, Darwin, Australia
wang@@menzies.su.edu.au