TABLE 1

Methods and Systems for A1C Testing and Their Susceptibility to Interference From Hb Variants (17,18)

Number of methods available for A1C tests5
Number of A1C testing system manufacturers∼70
Number of systems developed to measure A1C (including multiple versions of the same system)∼239
Number of systems available in the United States (including multiple versions of the same system)∼156
Number of systems evaluated and reported by NGSP as using robust methods37 (∼16% of all systems)
Number of these robust studies in which there was interference of results by Hb variants (C, S, E, D, elevated F, and carbamylated Hb)21 (57% of robustly evaluated systems)
Number of these robust studies reporting interference by HbS19 (51% of systems evaluated using robust methods)