Dear all,
I need to study specificity and sensitivity of measures of lymphocytes.
The gold standard is measures of CD4
A subject is diseased if CD4<200 and non diseased if CD4>=200
We want to study specifity and sensitivity for different threshold of
lymphocytes
Generally, if lymphocytes is <1200, subject is diseased.
Using the command
"roctab CD4_bin lymphocytes"
With CD4_bin=1 if CD4<200 and CD4_bin=0 if CD4>=200
I obtain graph and table for sensitivity/specificity for threshold of
lymphocytes in ascending order.
Or I'm interested in descending order: a patient is diseased if lymphocytes
is <1200, and not >=1200
If I use
gen inv=-1*lymphocytes
roctab CD4_bin inv
It's OK, but the table is not useful because of negative values of
lymphocytes
Thanks for help
A.Bissery
*****************************************************
Alvine BISSERY
Ingénieur statisticien
Service de Biostatistique des Hospices Civils de Lyon
162 Avenue Lacassagne
69424 Lyon Cedex 03 - France
tél: +33 4 72 11 57 55
fax: +33 4 72 11 51 41
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
