# Diagnostic performance of 1-hour plasma glucose and glucose curve shape during oral glucose tolerance test: a cross-sectional study in a Brazilian cohort

## TL;DR

This study shows that measuring blood glucose 1 hour after a glucose load detects more cases of early diabetes and prediabetes than traditional methods in a Brazilian population.

## Contribution

The study introduces the 1-hour plasma glucose as a more effective early detection marker for dysglycemia compared to conventional methods.

## Key findings

- 1-hour plasma glucose identified 27.8% more intermediate hyperglycemia/diabetes cases than fasting glucose.
- Monophasic glucose curves were more common in individuals with impaired glycemic profiles.
- 1-hour glucose thresholds of ≥8.6 mmol/L and ≥11.6 mmol/L showed higher diagnostic performance for dysglycemia.

## Abstract

The 1-h plasma glucose (1-h PG) during oral glucose tolerance test (OGTT) may enhance early dysglycemia detection compared with conventional markers. Distinct glucose curve morphologies correlate with glycemic profiles, insulin sensitivity, and β-cell function. We aimed to compare 1-h PG diagnostic performance with conventional methods and explored glucose curve morphology prevalence in a Brazilian population.

This retrospective cross-sectional study analyzed 1,797 OGTT records from a Brazilian laboratory (2021–2024). Glycemic profiles were classified using 1-h PG, fasting plasma glucose (FPG), 2-h PG, and HbA1c according to American Diabetes Association, Brazilian Diabetes Society and International Diabetes Federation criteria. Cohen's κ assessed inter-method agreement, McNemar’s chi-square tests compared high glycemic risk detection and χ2 tests evaluated associations between curve patterns (monophasic, biphasic, continuous rise) and glycemic status.

Participants were predominantly female (68.9%; mean age 49.6 ± 15.0 years). The 1-h PG identified 27.8% more intermediate hyperglycemia (IH)/type 2 diabetes mellitus (T2DM) cases than FPG, 16.8% more than 2-h PG, and 26.7% more than HbA1c. The 1-h PG identified more individuals at high glycemic risk than FPG (χ2 = 290, p < 0.001), HbA1c (χ2 = 129, p < 0.001), 2-h PG (χ2 = 165, p < 0.001), and their combined criteria. Among 1361 evaluable curves, 59.6% were monophasic, 38.3% biphasic, and 2.1% continuous rise. Monophasic curves predominated in IH/T2DM, whereas biphasic curves were more frequent in normoglycemia (χ2 = 278; P < 0.001).

The 1-h PG thresholds ≥ 8.6 mmol/L (155 mg/dL) for IH and ≥ 11.6 mmol/L (209 mg/dL) for T2DM identified more dysglycemia cases than conventional methods, supporting early detection utility. Monophasic curve morphology was associated with impaired glycemic profiles, highlighting prognostic relevance.