proc phreg

发布网友 发布时间：2023-04-27 13:48

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热心网友 时间：2023-10-23 10:59

One day, my boss took a glance at a table with Hazard Ratioand Median Survival Timethen he told me the program set the reference group in Proc Phregwrong.

It turns out he was correct after validating the program. However, I was very curious about how did he figure it out by an Augenblick. Then he shared with us some knowledge about Hazard Ratioand Proc Phreg.

Hazard Rate : HRs represent instantaneous risk over the study time period.

Median Survival Time: The time after which 50 percent of people with a particular condition are still living, and 50 percent have died.

Median survival time and Hazard Rate

if Median(A) > Median(B) then Hazard Rate(A) < Hazard Rate(B), vice versa.

Without Loss of Generality, if the median survival time of group A is significantly longer than group B, then Hazard Rate of group A is smaller than Hazard Rate of group B at any given point, vice versa.

qimono / Pixabay[/caption]

Now we will demonstrate Proc Phreg with Hazard Ratio with Sashelp.BMTdataset.

Basic Proc Phreg Syntax

<pre class="EnlighterJSRAW" data-enlighter-language="sql" data-enlighter-highlight="2,4">Proc phreg data=a;
class x ; / ref(x) only character value, the lowest character value is reference /
model x y= a/rl ; / can input more than one variable on the RHS of the equation. rl:risk limit (eßt) /
by z;/ optional /
id m;/ optional*/
run;</pre>

<pre class="EnlighterJSRAW" data-enlighter-language="sql">data aml;
set sashelp.bmt;
if group="AML-Low Risk" then ref="0";
if group="AML-High Risk" then ref="1";
if ref in("0","1");
run;</pre>

<pre class="EnlighterJSRAW" data-enlighter-language="sql" data-enlighter-highlight="2,3">proc phreg data=aml outest=est61 covout;
class ref;
model T*status(0)=ref/rl;
run;</pre>

Results:

From the output, we have Hazard Ratio=0.39, which means the risk of death of a patient in AML high Group survives until today and will survive until tomorrow, compared with the AML Low Group Reced by 0.61. (1-Hazard Ratio)*100%

Validation:

As we mentioned earlier, if Hazard Ratio <1 then we expected a longer survival median time in AML Low Group. The following Kaplan Meier plot demonstrated the AML Low Group indeed has a larger survival median.

<pre class="EnlighterJSRAW" data-enlighter-language="python">proc lifetest data=aml plots=survival;
time T*status(0);
strata Group;
run;</pre>

Thanks very much to Joe wang to share the Proc Phreg knowledge with me, we will show the 3-level Hazard Ratio in Proc Phreg next time!

Happy studying! 🐰