CGM can be a useful diagnostic tool for cystic fibrosis diabetes, but data are scarce

A new review of studies comparing continuous glucose monitoring (CGM) to oral glucose tolerance testing (OGTT) suggests that continuous monitoring would flag more people with cystic fibrosis than cystic fibrosis diabetes (CFRD), but the authors said the The existing research base is too fragmented to know how to ensure accurate diagnoses with CGM.

Previous research suggests that up to half of people with cystic fibrosis will develop diabetes, and the comorbidity can lead to a range of complications, including a higher risk of infection, more rapid lung deterioration, and ultimately higher mortality. Early detection of CFRD is considered crucial as treating CFRD can lead to improved lung function and lower mortality rates.

CGM is a technology that tracks patients’ blood glucose levels over time. It was developed to help patients with diabetes manage their disease, but corresponding author Helena Teede, MBBS, PhD, of Monash University in Australia, along with colleagues, explained that the technology could theoretically also be used to detect patients with CFRD could be employed, leading to earlier treatment and improved long-term outcomes.

In a new review article in the Journal of Clinical and Translational EndocrinologyTeede and colleagues analyzed the existing scientific literature to find studies comparing CGM to OGTT as a tool to detect dysglycemia in people with cystic fibrosis.

The authors found a total of 19 studies that included CGM and OGTT metrics. A total of 416 patients were included in the studies. On CGM, hyperglycemia was defined as at least one peak sensor glucose reading of at least 200 mg/dL, and dysglycemia was defined as at least one peak sensor glucose reading between 140 and 199 mg/dL.

“CGM hyperglycemia in people with normal or abnormal glucose tolerance has been used to define an arbitrary CGM diagnosis of diabetes,” explained Teede and colleagues.

Although the researchers attempted to compare the results between CGM and OGTT diagnosis, Teede and colleagues said they chose not to characterize the results as superior or inferior, or as having higher or lower sensitivity because there was not yet any international consensus on the use of CGM to screen or diagnose people with CFRD and because there is no third reference against which to compare CGM and the current gold standard OGTT.

A comparison of the data in the 16 studies showed that the relative risk of an arbitrary CGM diagnosis of diabetes compared to the OGTT was 2.92, but Teede and colleagues cautioned that the studies they analyzed were very heterogeneous and prone to bias.

The researchers said that CGM’s ability to collect long-term data makes it a useful tool to capture a spectrum of glucose abnormalities in people with cystic fibrosis. Still, they concluded that a single CGM reading of 200 mg/dL is insufficient to diagnose a patient with CFRD.

Teede and colleagues concluded that more studies are needed to better understand the role CGM could potentially play in monitoring and diagnosing diabetes in people with cystic fibrosis.

“To enable high-quality research in this area, first reporting of standardized CGM metrics and consensus on definitions for CGM measures of dysglycemia and hyperglycemia in PwCF would be helpful,” they wrote.

In addition, the authors said that long-term prospective studies would help researchers make better connections between CGM interventions and disease-specific outcomes. They added that data assessing consumer and healthcare provider experiences would aid in policy development and translation of CGM into clinical practice.

Relation

Kumar S, Pallin M, soldatos G, Teede H. Comparison of continuous glucose monitoring to the oral reference standard glucose tolerance test for the detection of dysglycemia in cystic fibrosis: a systematic review. J.Clin. translation Endocrinol. 2022;30:100305. Published September 27, 2022. doi:10.1016/j.jcte.2022.100305