Minimum samples for q6 month correlations

The minimum sample number required by for your semi-annual correlation studies is set by what your MD is comfortable with.  Factors that play into this can be:  how long you've had it, how stable it is, how much you trust it, how challenging it is to obtain specimens.

Most tests correlations we do 10 samples, one test that we've been using for over 15 years and is very stable we only do 5.
Initial validations we do anywhere from 20 to 100, again depending on the test and results obtained.

We do three challenges -  twice per year to follow what CAP uses for quality cross check. There is a template on cap.org that is available to cap accredited sites that has 13 rows. CAP recently had a Focus on Compliance webinar that spoke about Laboratory Statistical Analysis. When the topic of Comparability of Instruments and Methods was being discussed, the example showed 5 samples.

Our medical director approved using 3 samples twice per year. I wouldn't feel comfortable doing less than what CAP expects but one could always do more.

Hope this helps!
Erika 

I agree with Jeremy and Erika. Whatever your medical director sets, and is policy, just follow the policy.  We do 5 samples here. 

Our minimum is 5 also.  I usually get around 10 due to trying to span the analytes test range.