The mission of the Micronutrients Measurement Quality Assurance Program (M(
2)QAP) at the National institute of Standards and Technology is enhanced in
terlaboratory measurement comparability for fat-soluble vitamin-related mea
surands in human serum. We recently described improved tools for evaluating
individual participant measurement performance in single interlaboratory c
omparison exercises; we here apply and extend these tools to the evaluation
of participant performance over the entire 15-year history of the M(2)QAP.
We describe and illustrate a set of interconnected graphical reporting too
ls for identifying long-term trends and single-exercise events. We document
and discuss recurrent patterns we observe in the measurement performance c
haracteristics for M(2)QAP participants. The graphical analysis techniques
utilized may he applicable to other interlaboratory comparison programs.