Novel Diagnostic Test Differentiates Type I from Type II Diabetes at an Early Stage

A novel DNA-based diagnostic test enables the early detection of type I diabetes while differentiating patients with type I diabetes from those with the type II form of the disease.

Type I diabetes mellitus is a T-cell mediated autoimmune disease in which deterioration of insulin producing pancreatic beta-cells leads to a state of insulin deficiency. Earlier studies have shown that the clinical symptoms of type I diabetes are preceded by the presence of islet cell autoantibodies (ICA) in the serum.

Radioimmunoassay (RIA) based detection of ICA is the current gold standard for diagnosis of type I diabetes. While the onset of hyperglycemia is an indicator of onset of diabetes, detection of ICA within the serum is important to differentiate type I diabetes from ketogenic type II diabetes. However, due to its limited range of sensitivity, RIA cannot detect ICA at low concentrations in serum, which could lead to delay in proper diagnosis and treatment. In addition, the use of radioactive materials presents major disadvantages including exposure, waste removal, need for specialized licensed facilities to conduct the tests and the time required for the test (more than 24 hours).

To overcome these limitations, investigators at Massachusetts General Hospital (Boston, USA) developed a rapid, highly sensitive, fluorescent and microsphere-based assay technique using rolling circle amplification (RCA), to profile marker antibodies for type I diabetes in serum. Rolling circle replication is a process of unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA, such as plasmids, the genomes of bacteriophages, and the circular RNA genome of viroids. Some eukaryotic viruses also replicate their DNA via a rolling circle mechanism.

The newly developed assay utilizes the ability of RCA to detect very small amounts of DNA coupled with microsphere-immobilization resulting in an assay that is at least 50 times more sensitive than RIA. Furthermore, this assay method requires a very low sample volume (five microliters), and can be easily adapted to detect other autoantibodies at similar sensitivities while reducing the overall assay time to approximately six hours.

"This is a clever combination of the several existing techniques, the result of which is a more sensitive, nonradioactive, clinically-relevant assay," said senior author Dr. Martin Yarmush, lecturer on surgery at the Massachusetts General Hospital. "It is our hope that this technique will become a useful tool for early detection of islet cell autoantibodies (ICA) in at-risk patients, which could lead to intervention before significant loss of islet cell mass."

Details of the method were published in the July 15, 2014, online edition of the journal TECHNOLOGY.

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