Stability Analysis: How do I back calculate release values necessary to support shelf life?Hello all,
I have recently been working with stability analysis (Degradation) and am running up against a wall with what should be fairly simple (I think).
I have a dataset from multiple lots and the data are poolable (valid for common slope, different intercepts). I am trying to back calculate what release values would need to be to still be within the lower spec limit at X months. I have the slope, but I'm not sure how to account for the confidence interval in the model. I feel like this should be a fairly simple lift but I cannot seem to find how to do this without brute-forcing numbers into the model until I get the right value.
I'm happy to do more legwork...just hoping that someone can point me in the right direction.
Thanks in advance!
Chris
Basic Data Analysis and ModelingQuality and Process EngineeringReliability AnalysisRe: Stability Analysis: How do I back calculate release values necessary to support shelf life?Hi Dave,
Thanks for the response. I think I wasn't explaining my situation correctly.
I have run the degradation script and have the common slope/different intercept parameters. I also have have the projected expiry based on the ICH limits, etc., from that pooled model.
I'm wanting to go in the opposite direction. Say, for example, that I have a lower spec limit of 1 mg/mL...and I want to know - based on the common slope AND accounting for the p=0.25 significance AND the 95%CI of the model - what my starting concentration would need to be for the model confidence interval to not drop below 1 mg/mL at a certain timepoint. I can get the answer by brute force...but I'm assuming that there's a better approach to doing this. For example, is it possible to save the model describing the lower 95%CI of the pooled fit and then do an inverse prediction, etc.?
Sorry I didn't go into more detail at first.
Chris
Re: Stability Analysis: How do I back calculate release values necessary to support shelf life?There is a data table Reliability/Stability in the Sample Data area.
If you run the degradation script you will see a model with common slopes and separate intercepts.
From the graph you can see the lower confidence bound of batch 2 (green) crosses the spec level at about time 4.5.
Open the Diagnostics and Predictions outline and there is a tab for Inverse Prediction. Either try and make sense of that graph or from the red triangle choose "Save Crossing Time".
Re: Stability Analysis: How do I back calculate release values necessary to support shelf life?Hi @ClusterFerret68 The ADG method of example 1 in the attached is how the RL is typically calculated throughout the industry.
http://www.mbswonline.com/upload/presentation_5-25-2012-10-45-1.ppt
Re: Stability Analysis: How do I back calculate release values necessary to support shelf life?Thanks @MRB3855 - I'll spend some time on this this evening.
Chris
Re: Stability Analysis: How do I back calculate release values necessary to support shelf life?Hi @ClusterFerret68 Using the fit model platform, you’ll have stability time-point and batch as effects. Batch should be set as random. You’ll then have all the inputs you need as shown in example 1.
