Diagnostic advantage of double immunohistochemistry using two mutation-specific anti-IDH antibodies (HMab-1 and MsMab-1) in gliomas.

Isocitrate dehydrogenase (IDH) mutation is a valuable prognostic marker and a tool for decision-making for glioma treatment. An algorithm for IDH mutation screening was recently proposed--it consists of a two-step process of an initial search for the most common IDH1-R132H mutation using immunohistochemistry (IHC)-based assay, followed by DNA-based analysis of IHC-negative or -equivocal cases. Here, we report that immunohistochemistry using two mutation-specific anti-IDH monoclonal antibodies (mAbs)--an IDH1-R132H-specific mAb (clone HMab-1) and a multi-specific mAb (clone MsMab-1)--is easy and reliable for IDH mutation screening. We investigated the IDH status of 54 grade III gliomas. For the first screening, we used HMab-1 IHC and for the second, (of HMab-1-negative cases) we used MsMab-1 IHC. The double IHC screening results were confirmed using sequence analysis (100% specificity and 100% sensitivity). Thirty of 54 cases (55.6%) had IDH mutations and the remaining 24 were of the IDH wild type; moreover, the screening results predicted grade III glioma prognosis. IDH sequencing procedures are popular but inconsistent across laboratories. By contrast, double IHC screening using HMab-1 and MsMab-1 is very reliable for detecting IDH1/2 mutations and can predict survival in grade III glioma patients.