Solved – How to combine two hazard ratios from the study for a meta-analysis

Question

I've been searching for a way to combine two hazard ratios from the same study for a meta-analysis, but found nothing. Does anyone know how to do this?

Any thoughts would be great.

Good Day,

Simon

Answer 1

Hazard ratios can be combined if you have their 95% confidence intervals.

For instance, in Stata, using the user command metan (type findit metan from within Stata if you don't already have it), you can use the following code in a do file to check out how the HRs can be combined:

clear all

input str6 trialname hr ll ul
    Trial1 0.7 .46 1.08
    Trial2 1.05 .82 1.34
    end

metan hr ll ul, effect(Hazard Ratio) null(1) xlabel(0, .5, 1, 1.5) ///
lcols(trialname) texts(200) force

Which gives the following output as well as a forest plot:

               Study     |     ES    [95% Conf. Interval]     % Weight
---------------------+---------------------------------------------------
Trial1               |  0.700       0.460     1.080         41.30
Trial2               |  1.050       0.820     1.340         58.70
---------------------+---------------------------------------------------
I-V pooled ES        |  0.905       0.706     1.105        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 

  Heterogeneity chi-squared =   2.87 (d.f. = 1) p = 0.090
  I-squared (variation in ES attributable to heterogeneity) =  65.2%

  Test of ES=0 : z=   8.91 p = 0.000

I hope this helps. If you don't use Stata, I'm sure any stats package can do a similar thing if you adapt the code.