# st: problem of stset and stsum

 From Jiqiong.You@nt.gov.au To statalist@hsphsun2.harvard.edu Subject st: problem of stset and stsum Date Fri, 11 Feb 2005 11:48:35 +0930

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Dear Statalist:

May I ask for help from stata experts?

I have a hospital data with patient ID (hrn), separation dates (sep_date) and
discharge status (dis_sta2, for those deceased coded as 1 others as 0).
The causes of admission in the data are classified as either CHD (cond=1) or
other (cond=0). The data contains at least one CHD admission for each patient.
There are 5882 subjects with 21299 admissions.

I am trying to analyse the survival of patients with CHD, using the following
statement. I came across the following problems.
1. The result shows that only 2519 subjects are left, originally there are 5882.
2. 'Stsum' doesn't show me the survival time at 25%, 50% and 75%.

Could anyone tell me why?

Cheers

Jiqiong

. stset sep_date, id(hrn) origin(cond=1) failure (dis_sta2=1)

id:  hrn
failure event:  dis_sta2 == 1
obs. time interval:  (sep_date[_n-1], sep_date]
exit on or before:  failure
t for analysis:  (time-origin)
origin:  cond==1

------------------------------------------------------------------------------
21299  total obs.
9839  obs. end on or before enter()
2062  obs. begin on or after (first) failure
------------------------------------------------------------------------------
9398  obs. remaining, representing
2519  subjects
0  failures in single failure-per-subject data
2360408  total analysis time at risk, at risk from t =         0
earliest observed entry t =         0
last observed exit t =      3561

. stsum

failure _d:  dis_sta2 == 1
analysis time _t:  (sep_date-origin)
origin:  cond==1
id:  hrn

|               incidence       no. of    |------ Survival time -----|
| time at risk     rate        subjects        25%       50%       75%
---------+---------------------------------------------------------------------
total |      2360408          0          2519          .         .         .

. qui sort hrn sep_date

. qui by hrn: gen n=_n

. qui by hrn: gen N=_N

. sum one if n==1

Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
one |      5882    1.984189    1.846311          1         16

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