Monday, February 17, 2014

More on Predicting the Future in IPF

John R. asked the following question:

"What is your take on using the GAP Risk Assessment System as a tool to help determine a basic prognosis for the IPF patient?"

Here's my answer:

Thanks for bringing up the GAP score, John. For those who don't know about the GAP score, it is a simple tool that combines Gender, Age, and Pulmonary function test results (see the G-A-P there?) to help doctors predict how likely it is that someone with idiopathic pulmonary fibrosis (IPF) might die over the next three years.

The GAP score is an accurate tool that helps us identify people with IPF that should be considered for enrollment in clinical trials of new treatments or who might need lung transplantation. But the GAP score, just like any other prediction of the future, can't tell us what is going to happen to an individual person. Here's an example of what I mean.

Imagine that someone's GAP score was "4". About 1 out of 3 people with a GAP score of 4 will die over the following two years. This might mean that we should consider lung transplantation or enrollment in trials of new treatments -- in this way, the GAP score is indeed helpful. But this information actually does not help us know how long someone has left. Are you one of the "1 out of 3"? We still don't know the future.

Bottom line: Risk prediction tools like the GAP score can be very helpful for making decisions about treatment options, but are not really helpful if the question you are asking is "when am I going to die?" They can't answer those questions unless they predict a very high (>95%) or very low (>5%) risk, and in most cases, we don't need risk prediction tools when your risk is very high or very low, because it is often quite obvious when someone is very sick or very well.

While I do NOT recommend calculating your GAP score (for the reasons discussed above), I know everyone has already googled it. Here is a link to the calculator.

One more thing: the GAP score was developed in idiopathic pulmonary fibrosis (IPF) and may not apply to all of the other forms of Pulmonary Fibrosis. Many other forms of Pulmonary Fibrosis have better outcomes than IPF.

5 comments :

  1. Very interesting. Just one problem. I don't see that link to the GAP calculator. Missing from the version I'm reading.

    Harold P. Morgan
    hpmsrm@sbcglobal.net

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  2. Thank you Dr David for clarifying the practicality of the GAP score. And thank you John R for bringing up this question.

    I think you forgot the link though, Dr David, so here it is.

    http://www.acponline.org/journals/annals/extras/gap/

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  3. Thank you Dr. Lederer for taking the time to post such a well articulated reply to my question. I was first diagnosed with PF 12 years ago via a CT Scan with Contrast. This past August I received my IPF dx via a VATS Biopsy. I'm a numbers kinda guy and the GAP calculator put things into a perspective that I can understand. The numbers are in my favor :)

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  4. I don't know what my mom's GAP score would have been back in 2003 at diagnosis. She was 64 at the time, had a DLCO of 27%. I can't remember what her FVC was. She was very sick. In Congestive Heart Failure. Given 2 years to live. She lived for 6. Diagnosed with IPF by biopsy. Dr. Raghu and I both felt a lot her living so long, and doing so well during that 6 years, was her attitude. She had this "I'm not giving up until I am darn good and ready" attitude. She stayed positive and she stayed healthy in every other way possible. But I think she may have blown her GAP score out of the water. :-)

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  5. Thanks Harold and Barbara. The link should now be clickable in the post. Thanks also to JR for the question. And Taleena, your mom's story proves the point I tried to make in this post. Thanks for sharing your mom's experience here.

    David

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