Diagnostic testing for IDH1 and IDH2 variants in acute myeloid leukemia: An algorithmic approach using high-resolution melting curve analysis

Isocitrate dehydrogenase 1 (IDH1) and IDH2 mutations and polymorphism are reported in 5% to 15% of acute myeloid leukemia (AML) cases, with G105 and R132 of IDH1 and R140 and R172 of IDH2 known to be clinically significant. Current Sanger sequencing assays to detect IDH mutations are labor intensive and not cost effective for clinical testing of low-frequency mutations. Therefore, we developed clinical assays using high-resolution melting (HRM) analysis to screen for all four variants listed above, followed by Sanger sequencing confirmation. The sensitivities of the assays were 7.3% and 7.9% for the detection of IDH2 and IDH1 variants, respectively, against the background of wild-type transcripts. Comparison of HRM to Sanger sequencing on 146 AML bone marrow samples for validation showed near-perfect concordance for all positive and negative results for IDH1 (98%) and IDH2 (94%). Postvalidation clinical implementation of upfront HRM screening (N ∇ 106), using a more conservative algorithm to avoid false-negative results, reduced the number of Sanger sequencing tests by 73% (IDH1) and 78% (IDH2). Of the variant calls made by HRM in postvalidation clinical samples, Sanger confirmed the presence of a variant in 62% (IDH1) and 44% (IDH2) of the samples. In conclusion, our HRM assays are rapid, convenient, and versatile assays for screening and confirmation of alterations in IDH1 and IDH2.