Assessing the Utility of a Capillary-Adjusted Oral Glucose Tolerance Test for the Early Detection of Type 1 Diabetes in Childhood

OBJECTIVE: The oral glucose tolerance test (OGTT) is the gold standard for staging and monitoring type 1 diabetes (T1D), but it requires venous sampling in a health care setting, limiting its accessibility. We assessed the utility of a capillary-adjusted OGTT (cOGTT) method in children and young people (CYP). METHODS: Study 1-OGTT method comparison: CYP across the glycemic range underwent contemporaneous venous (vGluc) and capillary (cGluc) glucose sampling at 0-min, 60-min (subgroup), and 120-min after a standard oral glucose load. Agreement between vGluc and cGluc was assessed using Bland-Altman between 3.5 and 15 mmol/L. Glycemic status was assessed using established thresholds and acceptability by questionnaire. Study 2-At-home OGTT feasibility: CYP with early-stage T1D undertook home cOGTT testing (0, 120 min) and completed acceptability questionnaires. RESULTS: Study 1: Forty-five CYP participated (mean [SD] age 12.2 [3.2] years; range 5-17), with 20 undergoing additional 60-min sampling. cGluc and vGluc showed reasonable agreement across the glycemic range of 3.5-15 mmol/L, (bias, -0.22 mmol/L; 95% confidence interval [CI]: -0.51 to 0.07; 95% limits of agreement, -2.91 to 2.47 mmol/L). cGluc performed well at normoglycemia: 21/22 (95% sensitivity; 95% CI: 77%-100%), 14/17 (82% specificity; 57%-96%); and hyperglycemia: 9/10 (90% sensitivity; 55%-100%), 29/29 (100% specificity; 88%-100%); but less well for dysglycemia: 4/7 (57% sensitivity; 18%-90%), 30/32 (94% specificity; 79%-99%). In 76% (32/42), cOGTT was preferred for future testing. Study 2: 45 CYP participated (10.4 [3.1] years; range 4-17). In 91% (41/45), home cOGTT tests were completed successfully (3 device failures, 1 incomplete test). Home testing was acceptable in 98% (44 of 45). Two CYP were identified with stage 3 T1D with no evidence of DKA. CONCLUSIONS: The cOGTT method is feasible and acceptable compared with venous OGTT in CYP, with promising performance for detecting hyperglycemia, but further assessment is needed before it can be used for glycemic staging.