You are here: Home > Lab Q A > Fixed Limits

Whats New...

Fixed Limits (February 2003)

The 'Fixed Limit' criteria was implemented for Chemistry method evaluation in January 2002. The fixed limits derived according to CG Fraser, were based on biological variation data.

As anticipated, several fixed limits were too tight and an excessive number of analytical failures have occurred. The fixed limits have been broadened to compensate for variation in manufacturer methodologies, and the lack of standardization relative to a reference method when measuring the true analytic value.

It is the proficiency testing providers intent, to continue to monitor these adjustments, and as manufacturers standardize their methods, the limits will be notched back to align them with Fraser's recommendations. This alignment of methodologies is in the development stages for most manufacturers, and is due to the European directive, 'that all methods used in the European countries, must be standardized to a reference method by 2003'.

This extension to the fixed limits prevents laboratories from being penalized inappropriately. As improvements are made to analytic measurements, the goal of a common standard of accuracy will be achieved.