Urinary proteins: up-to-date reference methods for urinary protein analysis.

Measurement of urine albumin has been introduced in the new classification of kidney disease (KD) as a marker for detecting, monitoring and predicting K.D. Currently, the measure is not standardized. The variability of results obtained with commercially available procedures is important and can lead to misclassification of patients. Analytical standardization, started in 2007, is in progress. SRM 2925 primary reference material, SRM 3666 secondary reference material and liquid chromatography isotope dilution mass spectroscopy (LC-IDMS) reference measurement procedure are being validated by the National Institute of Standards and Technology (NEST). This report presents strategies and difficulties for developing this reference system.