Although the correlation of the ARCHITECT insulin assay with the E-test TOSOH II (IRI) was good across the clinical measurement range, we detected slope deviation.
In the comparison test, however, we observed slope deviation.
cause of the slope deviation, it does suggest the influence of a matrix component and the need for further investigation.
A general, simplified formula for the approximation of the necessary sample size for detection of a difference [DELTA] with regard to slope deviation from unity or intercept deviation from zero (16) is:
With regard to the slope, this value refers to the slope deviation from unity measured in [CV.
Relating the systematic difference to a slope deviation corresponds to a demand of detecting [beta] = 1.
To get the necessary sample size, we consult Table 1 and look under a range ratio of 2 and a standardized slope deviation of 4 and find the sample size, N = 41.
Thus, in this example, the sample size requirement with regard to testing for intercept deviation from zero is less demanding than that of testing for a critical slope deviation.
For example, detection of one standardized slope deviation with the given type I error and power requires >500 samples when the range ratio is 2, but only 37 samples for a range ratio of 50 or higher.
Ascribing the systematic difference to a slope deviation implies a demand of detecting [beta] = 1.