What is interassay coefficient of variation?

Answer 1

The formula for coefficient of variation is %CV = standard deviation/mean X 100 (CV's are reported in percentage form).

So say you're testing for fibrinogen in blood, and you run your standards or your controls three times. The INTRAassay CV is the CV for the three sets of standards in that one assay. You would calcuate the mean and standard deviation for Standard 1, Standard 2, etc. and come up with the CV for each and then average the CVs of each standard to come up with the intraassay CV. This shows the amount of variation among the standards for that one test.

Now say you run a set of blood samples on Monday and then run another set on Tuesday with a second set of plates or wells. The INTERassay CV is the amount of variation between the standards you used on Monday and the standards you used on Tuesday. You would calculate the mean and standard deviation for Standard 1 (Day 1 and Day 2), Standard 2 (Day 1 and Day 2), etc. to come up with the CV for each and then average the CVs like before. This gives you the interassay CV.

A lot of ELISAs will actually calculate the CV of each standard for you.