- Once approved, a Technical Letter  becomes an i ntegral part of the ISL and supersedes any previous publication on a similar topic1, including Technical Document (s) and/or the ISL ; - The implementation of the requirements of relevant Technical Letters  into the Laboratory ’s and, if relevant to the analysis of ABP blood Sample s, the ABP Laboratory ’s Management System is mandatory for obtaining and maintaining    ISL – January 2021 Page 11 of 160 WADA  accreditation or approval, respectively, and for the application of the relevant Analytical Testing  Procedure (s) to the analysis of Samples.