Fraity Model with PhReg

iuri_leite — Mon, 06 Nov 2023 20:29:45 GMT

Dear All,

We are analyzing data from a cohort of participants with a high risk of HIV infection. At this moment, our focus is on sexually transmitted disease infection. Given that patients in our cohort may have more than one sexually transmitted disease, we are considering using a frailty model.

We are currently thinking of using the COX Regression model, but I would like to check if the data structure I am creating is correct.

The structure of our database would incorporate time-dependent variables.

Here we have the data for three participants. The observation of the participant 1 (ID=1) is censored at the first visit, then he experiences the event at the second visit, and does not return. The second participant experiences several events while the third one is censored at all visits.

ID TSTART TSTOP STATUS

1 0 91 0

1 91 187 1

2 0 115 0

2 115 210 1

2 210 321 0

2 321 430 1

2 430 542 1

3 0 122 0

3 122 312 0

3 312 431 0

The other issue I wanted to address is how to decide on the distribution of the random parameter associated with frailty. Is there a specific test for this?

Thank you..

Best regards,

Iuri leite

Re: Fraity Model with PhReg

sbxkoenk — Tue, 07 Nov 2023 16:45:55 GMT

Hello,

I am not an expert in frailty models (for sure not in practice), but here's some info.

The PHREG procedure in SAS implements the penalized likelihood method for the gamma and log-normal frailty models.
SAS/STAT 15.3 User's Guide
The PHREG Procedure
The Frailty Model
https://go.documentation.sas.com/doc/en/pgmsascdc/9.4_3.5/statug/statug_phreg_details16.htm
Paper 1492-2014
Introduction to Frailty Models
John Amrhein, McDougall Scientific Ltd.
https://support.sas.com/resources/papers/proceedings14/1492-2014.pdf
If you encounter recurrent disease episodes in patients, then this paper may be of interest:
Analysis of Correlated Recurrent and Terminal Events Data in SAS®
Li Lu(1), Chenwei Liu(2)
1 The EMMES Corporation, Rockville, MD
2 Core Genotyping Facility, Division of Cancer Epidemiology and Genetics, Advanced Technology Program, SAIC Frederick, Inc., NCI-Frederick, Frederick, MD
https://www.lexjansen.com/nesug/nesug08/sa/sa16.pdf

BR, Koen

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Fraity Model with PhReg

Re: Fraity Model with PhReg