The GlycoMark test measures 1,5-anhydroglucitol (1,5-AG), which is an indicator of hyperglycemic excursions over the prior 1-2 weeks in patients with diabetes. Circulating serum levels of 1,5-AG decrease in response to significant hyperglycemia because glycosuria interferes with 1,5-AG reabsorption in the kidney tubules. Significant hyperglycemia and resultant glycosuria causes 1,5-AG levels to fall below the normal range (∼10 ug/mL), and persistent glycosuria is associated with very low 1,5-AG levels, less than or equal to 2 ug/mL. SGLT2 inhibitors elicit their effect by blocking glucose reabsorption, causing persistent glycosuria. A survey of clinical laboratory results in 2014 indicated that 13% of the GlycoMark 1,5-AG tests produced results of 2 ug/mL or less (unpublished, data on file). We hypothesized that the use of SGLT2 inhibitors (SGLT2i) would produce a high frequency of GlycoMark 1,5-AG results less than 2 ug/mL. A review of GlycoMark 1,5-AG measurements performed between January 2015 - April 2018 from 291 patients that were prescribed SGLT2i was performed. 35 patients were found to be non-compliant with their SGLT2i and were excluded from the analysis. From the remaining 256 patients taking SGLT2i, the average GlycoMark 1,5-AG level was 1.7 ug/mL and 87% of patients taking SGLT2 inhibitors had GlycoMark 1,5-AG values less than or equal to 2 ug/mL. The results of this analysis indicate that the majority of patients with diabetes that are taking SGLT2i have very low GlycoMark 1,5-AG results, which reflects the persistent glycosuria caused by the SGLT2i. In patients taking SGLT2i, a GlycoMark 1,5-AG result of 2 ug/mL may be useful as an indicator of the SGLT2i effect, particularly in patients with moderate to good glycemic control. Additionally, the average GlycoMark 1,5-AG level in the 35 non-compliant patients was 7.5 ug/mL, suggesting that GlycoMark test measurements above 2 ug/mL should be investigated for non-compliance, interference with, or reduced effectiveness of SGLT2i.
S.S. Fereidouni: Advisory Panel; Self; AstraZeneca, Janssen Pharmaceuticals, Inc. Consultant; Self; glycomark. Speaker's Bureau; Self; Amgen Inc., Janssen Pharmaceuticals, Inc., Merck & Co., Inc., Novo Nordisk Inc. T.P. Shows: None. C. Lessard-Chaudoin: None. K. Brabentz: None. R.E. Tenopala: None. J.R. Dahlen: Employee; Self; GlycoMark.