Hazard ratio vs incidence rate

bollibompa — Thu, 19 May 2016 09:15:46 GMT

Hi,

Usually when I perform Cox-regressions (PHREG - two treatment groups) the estimated hazard ratio is often quite similar to the ratio of incidence rates in each treatment groups.

I now run a PHREG (2 treatment groups) which resulteted in a HR of 1.5. When I compared it with the ratio of incidence rate, this ratio resultated in 2.0.

I have validated all number oand calculations and I now wonder why they can differ so much? Non-constant hazards?

Thanks in advance

Thomas

Re: Hazard ratio vs incidence rate

SteveDenham — Thu, 19 May 2016 17:37:24 GMT

Non-constant for 2 groups implies non-proportionality, in which case, PHREG might not be the best way to analyze your results. A key assumption of Cox regression is proportionality of the hazard rates. Another comparison to check this out is to compare the HR from PHREG to the Kaplan-Meier (nonparametric) estimate you can obtain from LIFETEST.

Steve Denham

topic Hazard ratio vs incidence rate in SAS Procedures

Hazard ratio vs incidence rate

Re: Hazard ratio vs incidence rate