Oral glucose tolerance testing at 1 h and 2 h: relationship with glucose and cardiometabolic parameters and agreement for pre-diabetes diagnosis in patients with morbid obesity

Background: One hour plasma glucose concentration (1hPG) during an oral glucose tolerance test (OGTT) may be an alternative to 2-h plasma glucose concentration (2hPG) in the identification of individuals at increased risk of hyperglycaemia, although its role is not fully understood.

Aim: We aim to investigate the relationship of these measures with other glucose parameters, as well as their relationship with cardiometabolic risk markers and the level of agreement for prediabetes mellitus diagnosis, in a sample of patients with morbid obesity.

Methods: We retrospectively evaluated 656 patients with morbid obesity without diagnosed diabetes. To define prediabetes with 2hPG, 2022 American Diabetes Association guidelines criteria were used, while for 1hPG, glucose ≥ 155 mg/dL was considered. Cohen's Kappa coefficient was used to assess the agreement between both measures of prediabetes mellitus diagnosis.

Results: A Cohen's Kappa coefficient of 0.405 (p < 0.001) was obtained. The 1hPG were positively correlated with homeostatic model assessment for insulin resistance (HOMA-IR) (ρ = 0.281, p < 0.001), fasting plasma glucose (FPG) (ρ = 0.581, p < 0.001), glycated haemoglobin (Hb1AC) (ρ = 0.347, p < 0.001) and were negatively correlated with homeostatic model assessment for cell-β function (HOMA-β) (ρ = -0.092, p = 0.018). 2hPG were also correlated with the same parameters, except for HOMA-β.

Conclusion: A fair agreement between 1 and 2hPG was verified. 1hPG criteria may be a useful indicator of β-cell dysfunction and insulin resistance in patients with morbid obesity without diabetes diagnosis.