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st: Meta-Analysis using --metan-- how to ensure comparison to ES=1 not ES=0
From
Belinda Butcher <[email protected]>
To
[email protected]
Subject
st: Meta-Analysis using --metan-- how to ensure comparison to ES=1 not ES=0
Date
Mon, 15 Oct 2012 14:14:02 +1100
Hi,
I use Stata/MP for Mac 11.2, dated 16 May 2012. All files are up to date.
I am using the --metan-- command (available from SSC: http://ideas.repec.org/c/boc/bocode/s456798.html) to combine the results of some oncology studies.
I am combining the hazard ratios for progression free survival, using the upper and lower confidence interals).
I am using the following command:
metan pfshr pfsll pfsul, effect("Hazard Ratio") fixed lcols(study author year treatment) double by(drug) astext(50) xlabel(0.2, 0.5, 1, 2, 5) textsize(100) title("RR of PFS") null(1) force
I need to compare the resultant overall HR to one, rather than zero. To do this, I have included "null(1)" in my command. However, when I run the command, I get a comparison to ES=0 (see output below).
Study | ES [95% Conf. Interval] % Weight
---------------------+---------------------------------------------------
A
1 | 0.680 0.590 0.780 12.38
2 | 0.758 0.661 0.869 10.33
Sub-total |
I-V pooled ES | 0.715 0.645 0.786 22.72
---------------------+---------------------------------------------------
B
3 | 0.493 0.418 0.581 16.83
4 | 1.190 0.720 1.960 0.29
5 | 1.100 0.570 2.120 0.19
6 | 0.720 0.620 0.840 9.24
Sub-total |
I-V pooled ES | 0.584 0.519 0.649 26.54
---------------------+---------------------------------------------------
C
7 | 0.540 0.420 0.710 5.32
8 | 0.680 0.570 0.800 8.45
9 | 0.540 0.440 0.660 9.24
10 | 0.692 0.617 0.776 17.68
| 0.590 0.480 0.720 7.76
Sub-total |
I-V pooled ES | 0.628 0.580 0.676 48.45
---------------------+---------------------------------------------------
D
11 | 1.210 0.820 1.800 0.47
12 | 1.410 0.960 2.070 0.36
Sub-total |
I-V pooled ES | 1.298 0.930 1.665 0.83
---------------------+---------------------------------------------------
E
13 | 0.690 0.490 1.140 1.06
14 | 1.010 0.610 1.660 0.41
Sub-total |
I-V pooled ES | 0.779 0.502 1.055 1.46
---------------------+---------------------------------------------------
Overall |
I-V pooled ES | 0.644 0.610 0.677 100.00
---------------------+---------------------------------------------------
Heterogeneity calculated by formula
Q = SIGMA_i{ (1/variance_i)*(effect_i - effect_pooled)^2 }
where variance_i = ((upper limit - lower limit)/(2*z))^2
Test(s) of heterogeneity:
Heterogeneity degrees of
statistic freedom P I-squared**
A 1.18 1 0.278 15.1%
B 16.03 3 0.001 81.3%
C 7.53 4 0.110 46.9%
D 0.28 1 0.596 0.0%
E 1.03 1 0.310 3.1%
Overall 46.85 14 0.000 70.1%
Overall Test for heterogeneity between sub-groups:
20.79 4 0.000
** I-squared: the variation in ES attributable to heterogeneity)
Considerable heterogeneity observed (up to 81.3%) in one or more sub-groups,
Test for heterogeneity between sub-groups likely to be invalid
Significance test(s) of ES=0
A z= 19.99 p = 0.000
B z= 17.64 p = 0.000
C z= 25.62 p = 0.000
D z= 6.92 p = 0.000
E z= 5.52 p = 0.000
Overall z= 37.75 p = 0.000
-------------------------------------------------------------------------
I have looked in Sterne's book on Meta-Analysis (Sterne J.A.C (2009) Meta-Analysis in Stata: An updated collection from the Stata Journal), but haven't been able to work this out.
Your help is appreciated.
Kind regards,
Belinda Butcher BSc(Hons) MBiostat PhD
Director - Biostatistics & Medical Writing
WriteSource Medical Pty Ltd
PO Box 1521
Lane Cove NSW 1595
M: 0418 286 014
E: [email protected]
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