Comparison of radioimmunoprecipitation with luciferase immunoprecipitation for autoantibodies to GAD65 and IA-2beta

Abstract

Objective: To compare the sensitivity and specificity of luciferase immunoprecipitation (LIPS) with radioimmunoprecipitation (RIP) for the measurement of autoantibodies to the type 1 diabetes autoantigens glutamic acid decarboxylase 65 (GAD65) and insulinoma-associated protein (IA)-2beta.

Research design and methods: Sera from 49 type 1 diabetic patients and 100 nondiabetic control subjects from Diabetes Antibody Standardization Program 2007 were used to screen for autoantibodies to GAD65. An additional 200 type 1 diabetic patients and 200 nondiabetic control subjects were used to validate the GAD65 results and screen for autoantibodies to IA-2beta.

Results: LIPS showed equal sensitivity and specificity to RIP for detecting autoantibodies to GAD65 and IA-2beta. Receiver-operating characteristic analysis revealed that the detection of autoantibodies to GAD65 and IA-2beta by LIPS and RIP were not statistically different.

Conclusions: The LIPS assay does not require the use of radioisotopes or in vitro transcription/translation and is a practical alternative at the clinical level for the RIP assay.

Figure 1

GAD65 autoantibodies as determined by LIPS (A) and RIP (B) and IA-2β autoantibodies as determined by LIPS (C) and RIP (D). Dotted lines represent 3 SDs above the mean of the nondiabetic control sera. E: ROC analysis showing the area under the curve for GAD autoantibodies by LIPS (0.929 [95% CI 0.875–0.964]) and by RIP (0.941 [0.891–0.973]). There was no statistical difference (P = 0.592). F: ROC analysis showing the area under the curve for IA-2β autoantibodies by LIPS (0.844 [0.804– 0.879]) and by RIP (0.807 [0.763–0.849]). There was no statistical difference (P = 0.062).