Your results will depend, in large part, upon the reference value assigned to the artifact(s) contained in the ILC/PT. See “What are reference values?” question above for how NAPT obtains its reference values. Since ILC/PTs are in constant circulation, it is necessary to periodically ensure that reference values have not changed. In the case where an artifact is recalibrated and the reference value is found to have changed, participant data is reviewed to identify when the drift occurred. If the drift is found to have occurred before your preliminary report was issued, your results will then be compared to the newly established reference values. This may lead to a pass on your preliminary report, but a failure on your final report.
NAPT strives to minimize the impact of drift by selecting quality artifacts, scheduling regular pivot checks and monitoring data submitted by participants for any sudden changes in measurement data.