RE: Breath test data modeling
Any thoughts on this one, please let me know if it needs more clarifications.
I am sharing part of the data set below:
C ID TIME AMT EVID C(t)
1 0 86 1 0
1 0.25 0 0 0.38
1 0.5 0 0 2.71
1 0.75 0 0 4.56
1 1 0 0 5.85
1 1.25 0 0 7.72
1 1.5 0 0 11.19
1 1.75 0 0 13.96
1 2 0 0
16.54
1 2.5 0 0 21.21
1 3 0 0
27.84
1 3.5 0 0 27.1
1 4 0 0
28.65
1 4.5 0 0 26.61
1 5 0 0
22.27
1 5.5 0 0 19.9
1 6 0 0
17.83
2 0 86 1 0
2 0.25 0 0 3.64
2 0.5 0 0 7.22
2 0.75 0 0 9.75
2 1 0 0 13.4
2 1.25 0 0 16.87
2 1.5 0 0 20.36
2 1.75 0 0 24.09
2 2 0 0
31.92
2 2.5 0 0 37.94
2 3 0 0
41.52
2 3.5 0 0 38.42
2 4 0 0
32.07
2 4.5 0 0 29.39
2 5 0 0
25.64
2 5.5 0 0 23.62
2 6 0 0
20.69
Thanks
Ramy Abdelrahman, MBBCh
Clinical pharmacology fellow
Mayo clinic
[email protected]<mailto:[email protected]>
Quoted reply history
From: [email protected] [mailto:[email protected]] On
Behalf Of Abdelrahman, Ramy A., M.B., B.Ch.
Sent: Thursday, February 18, 2016 1:21 PM
To: '[email protected]'
Subject: [NMusers] Breath test data modeling
Dear all,
We evaluate gastric emptying with a 13C-spirulina breath test, which was
validated against the gold standard (i.e., scintigraphy).
We are trying to apply the Wagner Nelson equation to analyze the 13C breath
excretion curves. However, in patients with delayed gastric emptying, the
absorption of 13C, hence peak breath excretion, has not occurred by them.
Therefore, we do not have a reliable breath elimination constant, which is in
the equation, in some patients with delayed gastric emptying. Collecting breath
samples for a longer duration is not practical
So we are trying to use mixed effect modelling to estimate Kel in patient with
delayed gastric emptying, however plasma observations are not available in our
data and we only have the rate of CO2 excreted in breath at each breath sample
and the amount of 13C in the meal
Any suggestions how to model this without having plasma observation in our
data?
The Wagner Nelson formula is written as:
F[t] = (Abreath(t) + C(t)/Kel)/Abreath(∞)
where F[t] is a fractional dose of the carbon label emptied, C(t) is the 13CO2
excretion rate (%dose ⁄ h)
Thanks
Ramy Abdelrahman, MBBCh
Clinical pharmacology fellow
Mayo clinic
[email protected]<mailto:[email protected]>