Predictive Value of 1-Hour Glucose Elevations during Oral Glucose Tolerance Testing for Cystic Fibrosis-Related Diabetes

Abstract

Background. In cystic fibrosis-related diabetes (CFRD) screening, oral glucose tolerance test (OGTT) thresholds for detecting prediabetes and diabetes are defined by the 2-hour glucose (2 hG). Intermediate OGTT glucoses, between 0 and 2 hours, that are ≥200 mg/dL are deemed “indeterminate,” although lower 1-hour glucose (1 hG) thresholds identify those at increased risk of type 2 diabetes in other populations, and may also better predict clinical decline in CF. Studies of 1 hG thresholds <200 mg/dL in people with CF are limited. Methods. A single center, retrospective chart review was performed of patients with 1 hG available on OGTTs collected between 2010 and 2019. In patients with ≥2 OGTTs, Kaplan–Meier analysis estimated likelihood of progression to CFRD based on a high vs. low 1 hG. In patients with ≥1 OGTT, mixed-effects models tested whether baseline 1 hG and 2 hG predicted growth and lung function trajectories. Results. A total of 243 individuals with CF were identified with at least 1 OGTT including a 1 hG, and n = 177 had ≥2 OGTTs. Baseline age (mean ± SD) was 12.4 ± 2.6 years with 3.2 ± 1.4 years of follow-up. Twenty-eight developed CFRD. All who developed CFRD had a 1 hG ≥ 155 mg/dL prior to 2 hG > 140 mg/dL. The average 1 hG was 267 mg/dL when 2 hG ≥ 200 mg/dL. In a subset with baseline 2 hG < 140 mg/dL, 1 hG ≥ 140 mg/dL conferred an increased 5 years risk of CFRD ( p = 0.036 ). Baseline 2 hG predicted decline in FEV1%predicted, but 1 hG did not. Conclusions. In youth with CF, 1 hG ≥ 140 mg/dl is an early indicator of CFRD risk. However, 2 hG, rather than 1 hG, predicted lung function decline.

An Update in Cystic Fibrosis-Related Diabetes in Children and Adolescents

“…Although the International Society for Pediatric and Adolescent Diabetes (ISPAD) guidelines recommend initiating CFRD screening at the age of 10 years, some studies propose an earlier start, either from the age of 6 years or after 3 years following the CF diagnosis. This is supported by data indicating that even at the age of 10, 55% of children already presented early glucose abnormalities [34]. High-risk patients with a 1-h glucose level exceeding 200 mg/dL (11.1 mg/dL) are advised to undergo more frequent screenings every six months [34].…”

“…This is supported by data indicating that even at the age of 10, 55% of children already presented early glucose abnormalities [34]. High-risk patients with a 1-h glucose level exceeding 200 mg/dL (11.1 mg/dL) are advised to undergo more frequent screenings every six months [34].…”

“…CFRD with fasting hyperglycemia: Noted when the fasting glucose levels are >7 mmol/L (>126 mg/dL) and the 2-h plasma glucose levels are ≥11.1 mmol/L (≥200 mg/dL) [4,14,31,34,36,37].…”

“…Hypoglycemia in CF patients might be linked to factors such as delayed initial insulin secretion, liver disease, malnutrition, gastrointestinal complications, and dysfunctions related to the incretin hormones [29]. In the context of adolescent CF patients, a 1-h glucose value equal to or exceeding 140 mg/dL is considered an early indicator of CFRD risk, while the 2-h glucose level is predictive of lung function deterioration [34].…”