The approach to this would be:

- create the new variable that identifies period (I'm not sure why you use more than one) (PERIOD) - create a new variable that equals the number of days between expected and actual visit (POFFSET) - SORT the data on patient ID, PERIOD and POFFSET - create a new variable to mark the first record you find for a given patient and period (MARK) You do the last two steps like this:

sort ID PERIOD POFFSET gen MARK=1 if (ID = ID[-1]) and (PERIOD=PERIOD[-1]) then MARK = 0

MARK will set to zero for the second visit for any patient in a period (because ID and PERIOD will be the same as previous)

Jamie

On 2012-08-27, at 3:11 AM, epidata-list@lists.umanitoba.ca wrote:

I have a “.rec” Epidata data set with patients with chronic diseases (Diabetes and Hypertension). I would like to undertake some analysis to determine what is happening on the patients at different periods of follow up. (Month 3, 6, 12........)

i.e. Glucose levels, BP, BMI.......

Each period I select (M3, M6, M12...) I give an allowance of + &- 10 days. (e.g. for M3=90 days from the day of enrollment, I select between day 80 and day 100). This is because patients did not always respect their appointment dates.

In the period selected (between day 80 -100) some patients for several reasons were seen more than once. I would like to select only one visit date in case of moth 3 follow up that is closest to the 90th day from date of enrollment .(e.g. a patient had a visit on the 80th day and 95th day, I want to select the 95th day visit which is closest to day 90).....

How do I do this with Epidata analysis?

NB: My variables are “enrolment date” and “visit date”

Kwal _______________________________________________ EpiData-list mailing list EpiData-list@lists.umanitoba.ca http://lists.umanitoba.ca/mailman/listinfo/epidata-list