Bioequivalence and Bioavailability Forum

Dear all,

I have a few doubts regarding ISTD variation:

1. How should ISTD variation in a batch be calculated?

2. How much ISTD variation is allowed in an analytical batch?

3. Somtimes it happens that, ISTD and analyte of interest(drug) response (area) varies together. The accuracy is calculated using D/IS ratio. So the back calculated concentration is good and the value (may be CC STD or QC) passes. So should this be considered in ISTD variation?

4. During subject samples analysis it is observed sometimes that, the value fits in the trend (rather the profile) of subject concentrations, but like above case 2 both drug and ISTD shows low reponse.

And should that sample be considered for Repeat analysis?

How should it be handled?

Thanks in advance,
Best regards,
Prashant