Quantification of human growth hormone in serum with a labeled protein as an internal standard: essential considerations.

To manage and inform diagnostic or therapeutic decisions, measurement results which are accurate, specific, and comparable between laboratories are required. Two challenges associated with this are the definition of the measurand and the commutability of the reference standard used. Once the measurand is defined, the next step in improving standardization is developing traceable quantification methods for proteins in biological fluids.