The CPRL analyzes GHB (HbA1c) by HPLC using Bio-Rex 70 resin following the existing CPRL method protocol and sets the initial calibration for the standardization program based on the "set-point" used in the DCCT. The CPRL must document an accepted level of precision (total imprecision <3%) following NCCLS EP5-A2 guidelines (1). Back-up Primary Reference Laboratories (PRLs) and Secondary Reference Laboratories (SRLs) calibrate their assays so that results from fresh blood specimens agree with the CPRL (see section 2. and 3. below). The CPRL administers a monitoring program for all certified PRLs, SRLs, and Level 1 Laboratories (outlined below in section 5.).

References:
1. NCCLS. Evaluation of Precision Performance of Quantitative Measurement Methods; Approved Guideline;Second Edition. NCCLS document EP5-A2 (ISBN 1-56238-542-9). NCCLS, 940 West Valley Road, Suite 1400, Wayne, Pennsylvania 19087-1898 USA, 2004.