The reference method value.

The basis for the achievement and the control of accuracy in routine testing is represented by a hierarchy of methods. Different materials are used for transferring accuracy and for monitoring traceability. In these two operations, unreliable results may be obtained by using different materials (e.g. clinical specimens and reference materials) when matrix-sensitive methods are being used, as is frequently the case with routine methods. Intermediate-level (reference) methods may help to bridge the gap between the highest and the lowest levels, by using clinical specimens for method comparisons. If non-commutable materials are used for calibration and control of routine methods, these should have system specific values, assigned with an appropriate experimental design, including appropriate use of clinical specimens. Setting up networks of reference laboratories to implement and run reference systems on an ongoing basis, appears to be the practical pathway to accuracy. Improvements should be directed to lowering the matrix-sensitivity of routine methods and increasing the commutability of reference materials.