Commutability still matters

[...]situations have been described in which the product calibrators of routine measurement procedures were traceable to a noncommutable reference material, causing lack of agreement for patient samples among the different routine procedures (4, 7-13 ). [...]contributing to the challenge are factors such as modification of molecular forms during processing of clinical samples, purification of biomarkers of interest, and alteration of the usual sample matrix when preparing materials or adding stabilizing agents.