Elevated 1-hour level proves significant despite 2-hour level within normal glucose tolerance range.
The current approach of screening for type 2 diabetes using the fasting metabolic state, while convenient, is not effective. In a recent review evaluating the status of screening for type 2 diabetes, M.M. Engelgau et al (2000) stated that one of the criteria for appropriate screening is that the tests should detect the preclinical stage of disease and that the tests be shown to be acceptable and reliable. The conclusion that current screening recommendations are not consistent with available evidence was briefly reviewed.
Evidence is accumulating that most people with a 54%–67% range of impaired glucose tolerance have fasting glucose in the normal range. Meta-analysis of 20 different European studies showed as many as 31% of those who were have diabetes according to post-challenge plasma glucose had normal fasting values and therefore would not have been detected by a screening procedure based upon fasting glucose measurements alone. In an analysis over more than 30 years of a large population assessed for all-cause mortality researchers, it was found that an elevated 2-hour glucose level indicated increased mortality risk, independent of the 1-hour level.
Previous studies have suggested that the 1-hour glucose level above 155 mg/dL is a better predictor of progression to diabetes than the 2-hour level. The researchers conclude that present findings, in conjunction with the other observations, suggest that individuals at high risk for developing diabetes could be identified earlier by measuring the 1-hour postload glucose level.
This study followed 2,138 individuals over a 33-year period. Researchers categorized the cohort by baseline 1- and 2-hour glucose levels: group A (1 hour ≤ 155 mg/dL and 2 hours < 140 mg/dL; n = 1,112); group B (1 hour > 155 mg/dL and 2 hours < 140 mg/dL; n = 449); group C (1 hour ≤ 155 mg/dL and 2 hours 140-199 mg/dL; n = 83); group D (1 hour > 155 mg/dL and 2 hours 140-199 mg/dL; n = 301). By August 2013, 51% of the study participants had died. Group D had the worst prognosis (73.8% mortality), followed by groups C (67.5%), B (57.9%) and A (41.6%).
Patients with a 2-hour glucose level less than 140 mg/dL but an elevated 1-hour glucose had a 28% increased mortality risk vs. patients with non-elevated 1- and 2-hour glucose levels, according to researchers. With group A as a reference, researchers found a gradual increased hazard for mortality by study group (HR = 1.28, 1.6 and 1.76, for groups B, C and D, respectively).
It was previously found that beta-cell function appears to be better preserved in those with a 1-hour level below 155 mg/dL, and declines when the 1-hour value exceeds this value and deteriorates incrementally with IGT and [type 2 diabetes].
A 1-h glucose value > 155 mg/dl predicts mortality even when the 2-h level is < 140 mg/dl. However, when the 2-h level is in the impaired glucose tolerance range, the hazard for mortality rises significantly independent of the 1-h value. Individuals at risk for developing diabetes could be identified earlier using the 1-h threshold value of 155 mg/dl, which could avert progression to diabetes and increased mortality.
- A 1-h glucose value > 155 mg/dl predicts mortality even when the 2-h level is < 140 mg/dl.
- An elevated 2-hour glucose level indicated increased mortality risk, independent of the 1-hour level.
- Patients with a 2-hour glucose level less than 140 mg/dL but an elevated 1-hour glucose had a 28% increased mortality risk
One-hour post-load plasma glucose level during the OGTT predicts mortality: observations from the Israel Study of Glucose Intolerance, Obesity and Hypertension. Diabet Med. 2016 Mar 21. doi: 10.1111/dme.13116. [Epub ahead of print]