Clinical Evaluation of IDH Mutation Status in Formalin-Fixed Paraffin-Embedded Tissue in Gliomas

Abstract

Background and Objective Determination of isocitrate dehydrogenase (IDH) 1/2 mutational status is crucial for a glioma diagnosis. It is common for IDH mutational status to be determined via a two-step algorithm that utilizes immunohistochemistry studies for IDH1 R132H, the most frequent variant, followed by next-generation sequencing studies for immunohistochemistry-negative or immunohistochemistry-equivocal cases. The objective of this study was to evaluate adding a rapid real-time polymerase chain reaction (RT-PCR) assay to the testing algorithm. Methods We validated a modified, commercial, qualitative, RT-PCR assay with the ability to detect 14 variants in IDH1/2 in formalin-fixed paraffin-embedded glioma tumor specimens. The assay was validated using 51 tumor formalin-fixed paraffin-embedded specimens. During clinical implementation of this assay, 48 brain tumor specimens were assessed for IDH result concordance and turnaround time to result. Results Concordance between the RT-PCR and sequencing and IHC studies was 100%. This RT-PCR assay also showed concordant results with IHC for IDH1 R132H for 11 of the 12 (92%) tumor specimens with IDH mutations. The RT-PCR assay yielded faster results (average 2.6 days turnaround time) in comparison to sequencing studies (17.9 days), with complete concordance. Conclusions In summary, we report that this RT-PCR assay can reliably be performed on formalin-fixed paraffin-embedded specimens and has a faster turnaround time than sequencing assays and can be clinically implemented for determination of IDH mutation status for patients with glioma.

Evaluation of the rapid Idylla IDH1-2 mutation assay in FFPE glioma samples

“…Other assay possibilities have been explored previously. For example, recent studies demonstrated the clinical utility of quantitative PCR and digital droplet PCR tests for determining IDH1/ IDH2 mutational status that had good concordance with IHC and NGS [ 9 , 10 ]. Digital droplet PCR (ddPCR) is a technique where a water-oil emulsion partitions the sample into many individual reactions so that either zero, one, or more target molecules are present in each independent reaction.…”