I used stptime to calculate person-time for persons who have certain levels
of liver enzymes arranged on a likert scale. Output below:
. stset censdate, id(patient) fail(died) origin(time consent)
id: patient
failure event: died ~= 0 & died ~= .
obs. time interval: (censdate[_n-1], censdate]
exit on or before: failure
t for analysis: (time-origin)
origin: time consent
----------------------------------------------------------------------------
--
7047 total obs.
89 obs. end on or before enter()
----------------------------------------------------------------------------
--
6958 obs. remaining, representing
6958 subjects
481 failures in single failure-per-subject data
7858551 total analysis time at risk, at risk from t = 0
earliest observed entry t = 0
last observed exit t = 1929
.
. tab astlevel if liverscore==0
4 Level AST | Freq. Percent Cum.
------------+-----------------------------------
AST<0.5 | 1340 36.65 36.65
AST 0.5<1 | 1726 47.21 83.86
AST 1<2 | 455 12.45 96.31
AST 2+ | 135 3.69 100.00
------------+-----------------------------------
Total | 3656 100.00
. stptime if noliverdx==1, by(astlevel) per(1000) dd(4)
failure _d: died
analysis time _t: (censdate-origin)
origin: time consent
id: patient
(342 missing values generated)
astlevel | person-time failures rate [95% Conf. Interval]
-----------+-----------------------------------------------------------
AST<0.5 | 1531153.0004 55 0.0359 0.0276 0.0468
AST 0.5<1 | 1973301.9990 94 0.0476 0.0389 0.0583
AST 1<2 | 518659.9998 36 0.0694 0.0501 0.0962
AST 2+ | 137030.0007 28 0.2043 0.1411 0.2959
-----------+-----------------------------------------------------------
total | 4160144.9999 213 0.0512 0.0448 0.0586
I have been asked to do a test between the different person-times. Is it
possible to do this in STATA?
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