--- Ziad El-Khatib <[email protected]> wrote:
> well my intention is to see how the progress is over time.
> to be clearer and more specific, to compare time took group of HIV
> patients with resistance at baseline versus group of HIV patients
> without resistance at baseline to show treatment failure.
> option 1) treatment failure due to baseline resistance
> option 2) treatment failure due to resistance development during
> treatment
> option 3) no treatment failure at all
> option 4) patient dropped out (maybe this can not be added here?)
If I understand you correctly you want to study time till treatment
failure, and see how that time is influenced by whether or not they
where already resistant. So resistence is an explanatory variable and
time till failure the explained variable. This is a pretty standard
survival analysis problem. One of the nice things about survival
analysis is that both not yet haveing experienced treatment failure at
the time that the study stoppend, and dropping out can be well handled.
However, in case of dropping out one must assume that the fact of
dropping out is unrelated to the probability of treatment failure (this
seems problematic).
A nice text on how to prepare your data for this analysis can be found
on this page by Stephen Jenkins:
http://www.iser.essex.ac.uk/teaching/degree/stephenj/ec968/
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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