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    A Question regarding the Kaplan Meier survival curve.




    Hello guys

    I have a set of epidemiological data for a group of patients whom were followed up for a specific time period. The mortality rate was easily calculated, however I am rather confused on how to perform the Kaplan Meier survival curve.
    I have both the SPSS (V-17)and the Epi info (V 3.5.1) software, could anyone please tell me which is the simplest way of getting that survival curve?
    I am having trouble filling the variables, I would appreciate some insight on this issue as well.

    Thanks in advance guys

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    Re: A Question regarding the Kaplan Meier survival curve.

    You should have your data in this kind of format:

    Code: 
    id  time  died
    1   27    1
    2   84    0
    In this case subject 1 was followed for 27 days (or months or whatever) and then died, whereas subject 2 was followed for 84 days and at the end was still alive, ie they were censored at 84 days.

    Then it's simply a case of telling your stats package which variable is the time variable and which is the "failure" (death etc) variable. In SPSS you can do this in Analyze -> Survival -> Kaplan-Meier survival analysis. I haven't used Epi info so I can't tell you how to do it there.

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    Re: A Question regarding the Kaplan Meier survival curve.

    thank you very much your advice really helped.
    I was able to make the graph with both Epi info and SPSS. one way I know I am doing things right is that both programs gave me the same curve lol.
    so I got this curve after entering the data.
    how would you interpret this graph?
    isn't it supposed to reach 0 survival probability? ( bottom of the y axis)
    Thanks in advance
    P.S. The graph is on the attachments.
    Attached Images  

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    Re: A Question regarding the Kaplan Meier survival curve.

    In terms of interpretation, it tells you what % were alive at any given time of follow-up (eg survival at 2 years was 93%). Survival will only go to zero if you have followed everyone until death; if there are censored observations then it won't go to zero.

    One problem with these curves is that the very right-hand part of the curve can be quite misleading (if there are only a few non-censored survivors), so a rule of thumb is to truncate the x axis at the point where you only have 10 survivors, or 10% of the original cohort, whichever is higher.

    I'd suggest re-scaling the y axis to go from 0 to 1 - it would be much easier to interpret. You could also relabel the y axis to go from 0% to 100% for the same reason.

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    Re: A Question regarding the Kaplan Meier survival curve.

    This really helped
    I was wondering if this curve could be applied in a cross sectional survey as I have read it almost everywhere that it is used in trials

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    Re: A Question regarding the Kaplan Meier survival curve.


    I suppose it depends on how you've constructed your survey - for example if you've studied the same group of people over time, you can create Kaplan-Meier curves - but you have the problem of "interval censoring" in which you lost a patient but you're not sure when.

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