Hello,
I am just a beginner of R 1.9.0. I try to construct a predictive score for the development of liver cancer in cirrhotic patients. So dependant variable is binanry (cancer yes or no). Independant variables are biological data. The aim is to find out a cut-off value which differentiate (theoratically) from normal to pathological state for each biological data.
A binary endpoing is not a good choice for this problem, as the time to diagnosis is very important. Unless you only have a biopsy at a single fixed time (e.g., 5 years post study entry) it would be good to consider for example a Cox proportional hazards model. And there are many reasons for not using a cutoff, as detailed in my book Regression Modeling Strategies.
How can I step in procedue to get a cut-off value (threshold) for each variable? I think I should try by ROC. But I'm not sure. If so, someone can lead me?
Besides not recommending the use of cutoffs on an overall predicted value, I think that using cutoffs based on separate analyses of predictors is even worse.
Frank
If not, someone can advice me how ?
Any advice will be cordially aprreciated.
Tin Tin Htar Myint Research assistant Liver unit Jean Verdier Hospital, Bondy France
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Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
