Islet Autoantibody Assays in Type I Diabetes can Replace ICA Test
Daniel Lazar, Naomi Weintrob, Natalia Abramov, Sara Assa, Konstantin Bloch, Regina Ofan, Hadassa Ben-Zaken, Pnina Vardi
Institute for Pediatric Endocrinology and Diabetes, Schneider Children's Medical Center, Petah Tikva and Felsenstein Medical Research Center, Tel Aviv University
Islet cell antibodies (ICA) continue to serve as the basis of the principal serological test for definition of active autoimmunity of beta-cells. Its disadvantages are the need for human pancreatic tissue and difficulty in obtaining quantitative results. In the past decade biochemically-defined beta-cell antigens were described, leading to the development of sensitive and specific autoantibody assays, to predict insulin-dependent diabetes mellitus (IDDM). We examined the value of combined biochemically-based serological assays, such as autoantibodies to insulin (IAA), glutamic acid decarboxylase (GADA) and ICA512 (ICA512A) to replace the traditional ICA assay.
Blood samples of 114 newly diagnosed IDDM patients, aged 125 yrs (range 2 months - 29 years) were tested for ICA (indirect immunofluorescence), IAA, GADA and ICA512A (radiobinding assay). The latter 2 assays were performed using recombinant human [35S]-labeled antigen produced by in vitro transcription/translation. We found that fewer sera scored positive for ICA and/or IAA (80.7%, 92/114) than for 1 or more of IAA, GAD, or ICA512 (88.6%, 101/114). We conclude that combined testing for IAA, GAD and ICA512 can replace the traditional ICA/IAA test to predict IDDM and is helpful in the differential diagnosis of insulin-dependent and noninsulin-dependent diabetes.