Metaprop 'by'

[Sarah Larney]

Hello all,
I'm using metaprop in Stata 13.1 for Windows to obtain pooled prevalence estimates. I can successfully get estimates and a forest plot when I use the syntax:

.metaprop numerator denominator, random

However, when I try to use the 'by' option:

.metaprop numerator denominator, random by(period)

I get an error message:

invalid syntax error r(198)

I tried using a numeric variable as the by variable (as the ‘period’ variable is a string), but still received the same error. Any thoughts on resolving this much appreciated!

Thanks,
Sarah

[David Fisher]

Sarah,

Just to confirm that I can recreate the error using the first example dataset in the metaprop help file.

In other words:

use http://fmwww.bc.edu/repec/bocode/a/arbyn2009jcellmolmedfig1.dta, clear
metaprop num denom, by(tgroup)

Looking at the trace, it seems it's an undefined global, $hmean, that's causing the problem. You may be able to kludge it as follows (referring again to the example dataset above):

ameans denom
global hmean = r(mean_h)
metaprop num denom, by(tgroup)

(N.B. If you specify an if or in condition to metaprop, you should also specify them to ameans.)


Alternatively, specifying the ftt option ("Freeman-Tukey Double Arcsine Transformation") to metaprop seems to avoid the error (that is, without the need for my kludge). However, I don't know enough about meta-analysis of proportions to be able to say whether this is appropriate for you or not. That is:

metaprop num denom, by(tgroup) ftt

Hope that helps,

David.

[Sarah Larney]

Thanks David. I will try this today.

Sarah