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July 20, 2020
Diagnostic testing could be the linchpin for developing precision prevention, therapeutics, treatments, and prognostics in diabetes, according to an international consensus report.
Precision diagnostics in type 1 and type 2 diabetes has made a great deal of progress, “but at this stage it remains more theoretical than practical,” Paul Franks, PhD, an adjunct professor at the Harvard Chan School of Public Health, Boston, and corresponding author of this report.
Type 1 diabetes might be reclassified into diabetes subtypes in the coming years. However, “additional diagnostic methods might be applied to improve the precision of type 1 and 2 diabetes without reclassification,” said Franks, who heads the genetic and molecular epidemiology unit at Lund University Diabetes Center, Malmö, Sweden.
The American Diabetes Association (ADA) Precision Medicine in Diabetes Initiative released this report in partnership with the European Association for the Study of Diabetes, the first consensus paper from major diabetes associations, Frank said.
“The concept of precision diabetes medicine is only just coming of age. We anticipate that the report will be the springboard for many other related initiatives,” added Frank.
Precision diagnostics in this area face a number of barriers and research gaps.
Currently, no immune-based test can sufficiently diagnose type 1 diabetes. Clinicians shouldn’t rely on test results, clinical features, or prior prevalence in isolation, the authors cautioned. Two factors might assist in defining etiological subtypes: the age in which an initial islet autoantibody appears, and type of antibody. Although genetic risk and genetic risk scores (T1D-GRS) for type 1 diabetes have been well established, “a high T1D-GRS will have low positive predictive value in patient populations where the overall prevalence of T1D is low, such as those aged >50 years when diabetes is diagnosed,” the authors explained.
A major limitation in a diagnosis of type 2 diabetes is that it excludes all known causes of chronic hyperglycemia, said Franks. A diagnosis of type 2 diabetes also doesn’t include measurement of the organ- or tissue-specific defects causing the hyperglycemia. Precision diagnostics that help assign a mechanism of action to diagnosis could aid in therapeutic decisions, he added.
“Categories based on cluster analysis at diagnosis can provide insights into likely progression, risk of complications, and treatment response” of type 2 diabetes, wrote the authors. A limitation of this approach is its reliance on a fasting C-peptide at the time of diagnosis. C-peptide assays aren’t used routinely in clinical practice and their reliability varies among labs. Biomarkers used to define these clusters may also evolve over time, influenced by treatment or the course of disease.
“Moreover, the current approaches for clustering in [type 2 diabetes] require continuously distributed data to be categorized, which typically results in loss of power. Thus, these methods do not yield good predictive accuracy, a major expectation in precision medicine,” noted the authors.
While readily available clinical features such as sex, body mass index and HbA1c results help predict treatment response and progression of disease, they also pose the disadvantage of changing over time. Genetic data for type 2 diabetes might help explain the etiological processes of disease—but lack the predictive accuracy to replace current delineative methods.
The authors recommended additional studies to help define type 1 and 2 diabetes subtypes and the best pathways to treatment.
“Many promising biomarkers and approaches may improve the precision with which diabetes is diagnosed. Importantly, any new diagnostic approach will need to be compared with existing approaches and shown to be more accurate” and more cost-effective, said Franks. There should be a focus not only on diagnosing diabetes, but also assigning the probabilities of developing micro and/or macrovascular complications.
“Focusing only on glycaemia is unlikely to be particularly useful for improved prevention and treatment,” added Franks.