Calculated NCA Parameters don't match provided data

I am using the sbionca function to compute the NCA Parameters but am getting outputs that don't match the data I've provided. The Cmax/Tmax that is calculated is the first peak observed rather than the maximum concentration observed over the timeframe. How can I fix this?

Answer 1

[Charu]

Hello,

You're correct in identifying that the “sbionca” function in MATLAB calculates “Cmax” and “Tmax” based on noncompartmental analysis (NCA), which by default considers only the first occurrence of the maximum concentration for “Cmax/Tmax”.

In your case, because it’s multiple dosing, the concentration profile has multiple peaks, and “sbionca” is taking the first of those as “Cmax”, even though there is a higher peak later.

One workaround that can be used is manually compute “Cmax” and “Tmax”:

[maxConc, idx] = max(concentrationData);    
Tmax = timeData(idx);                       
 

fprintf('True Cmax: %.2f at Tmax: %.2f hours\n', maxConc, Tmax); 

The best practice for repeated dosing is to use steady state “Cmax” or to compute “Cmax” of the final dose.

Here is the output for the sample data I used along with manual computation of “Cmax “and “Tmax”.

Hope this helps!

Answer 2

[Jacob Mathew]

Hey Alexis,

In the documentation, the Non Compartmental Analysis notes that for Sparse Multiple Dosing, "concentration data is collected from multiple individuals at each time point and then averaged to calculate NCA parameters for each group instead". You can reference the documentation below:

https://www.mathworks.com/help/releases/R2024b/simbio/ug/non-compartmental-analysis.html#bvfxoj9

In the NCA parameters screenshot you have provided, there are only 14 datapoints present which could be the reason the algorithm fails to identify the correct peak. The NCA example in the documentation plots a graph with much higher number of datapoints.