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From | Patrick Munywoki <pmunywoki@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | st: Interval censoring using intcens |
Date | Sat, 28 Jul 2012 09:29:15 +0100 |
Hi, I have been attempting to analyse interval censored time-to-event data with 'intcens' ado (Griffin et al 2006). My data arise from a longitudinal household-based study with nasal swab collections twice-a-week for a duration of 26 weeks regardless of their any symptoms. I want to be able to estimate the duration of infectious period for one of the viruses we detected. I have reduced the data to one observation per infection episode in order to use the 'intcens' command with t0 being the date last positive sample while t1 is the date of the next negative sample. I hope this data conversion to single observation per infection episode data is alright? My questions? 1. How do i interpret the coefficient given in the results below? intcens t0 t1 male, dist(exp) time nolog stata output Exponential distribution - log acceleration factors Uncensored 0 Right-censored 0 Left-censored 0 Interval-censored 188 Number of obs = 188 Wald chi2(1) = 0.00 Log likelihood = -1796.982 Prob > chi2 = 0.9990 Coef. Std. Err. z P>z [95% Conf. Interval] male -.0001871 .1470683 -0.00 0.999 -.2884356 .2880615 _cons 9.817517 .2234524 43.94 0.000 9.379558 10.25548 Note the actual interval between the dates t0 and t1 is on average(sd) 3.6 (0.98) days; median(IQR) 4 (3-4) days; and range 2-7 days. 2. Whenever i try using any other distribution this error message pops up. What could be the problem here? intcens t0 t1 male, dist(weib) time nolog initial values not feasible r(1400); 3. Is there an alternative method to the interval censoring which allows me to use the multiple records per person accounting for the interval censoring. I have tried stpm but not sure whether it allows for this. I would greatly appreciate your help , Many thanks, -- Patrick Munywoki * * 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/