Applicability of SPC to Intra and Inter Assay controls

[sway@tanox.com]

One of the questions that was recently given to me was if SPC is appliciable to intra and inter assey controls for biologics testing.

The best example is the inter assay control.  First, a standard curve is generated using "known" sample concentrations (3-5 tested from each sample).  Then a given sample (control) is tested 3-5 times giving a range for that sample.  The next time that an assay is run, a sample (control) from the same lot is tested along with any other samples to be tested in the same manner.

To continue with the testing, the once the raw data is generated, the value from the assay is determined from the standard curve.

It is my contention that the variablity and repeatability of the assay should be determined via SPC on the control sample.

Does this application truely fall under SPC or traditional statistical methods?

Shawn Way, PE
Engineering Manager

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