identifying diseases before a particular date

[Banke]

Hello everyone,

Please, I am monitoring patietns for 1 year: 6months before they start taking medications (start_date) and 6 months after (end_date). The first day of medication intake is the index_date. Each patient has unique start, index, and end dates. I am asked toidentify baseline characteristics of my patients 6 months before they start taking medications i.e before the index date.My data consists of multiple observations for each patient. I am trying to reduce these to observations occuring 6 months before the index date.I am confused at what to do. I will really appreciate your help. Thank you

My data looks like this

patient  start_date   index_date  end_date

1            04/2015    10/24/2015   04/2016

1            04/2015    10/24/2015   04/2016

1            04/2015    10/24/2015   04/2016

2           01/2015     07/17/2015   01/2016

2           01/2015     07/17/2015   01/2016

[ballardw]

You say "identifying diseases" in the title. Which of these dates relates to disease? Before which "particular date".

You must define characteristics in terms of the variables you share with us as we do not know any interpretation without your help.

[Banke]

Sorry for the confusion. The baseline characteristics i want to identify are age, sex, region, diseases they had in that period and medications they took. I am not really worried about the first 3 because they usually stay the same but they are likely to have fewer diseases and take fewer medications before the index date. The disease variables are like 10 e.g. icd1 icd2 icd3 icd4 etc. each icd variable have list of conditions the patients have. I dont know how to link this because the index, start, and end dates are fixed for each patient. But checking now, there is a medical treatment date variable. Is that what i will use to identify if the condition was diagnosed before the index date? There is also fill date for prescription.

Thank you

[ballardw]

Your example data should include enough information that you can point to variables and values to do the task. Which means how do we know what disease? What "particular date" ?

Do you have a SAS data set with the information? If not building one or more sets with the information is a first step.

[Banke]

I understand it better now, thank you