Comparison of diagnostic methodologies to detect chromosomal abnormalities.

Abstract

e14617 Background: Traditional technologies such as cytogenetics, FISH, and microarray (CGH) are utilized in most clinical laboratories. Next-Generation Sequencing (NGS) is a relatively new tool to evaluate the cancer genome. Applications of this method include assessing single nucleotide variants (SNVs), indel mutations, and copy number variations (CNVs), including some large chromosomal deletions or gains. Methods: We used a custom Discovery+LOH NGS panel (Agilent, Santa Clara) to determine the utility of NGS in detecting CNV and loss of heterozygosity (LOH) events. Thirty six patients with known DNA structural abnormalities and hematologic disease were tested using cytogenetics, the NGS panel, and CytoScan HD microarray. Results: As shown in the table, NGS detected all abnormalities reported by CGH. NGS failed to detect 14 abnormalities reported by cytogenetics, but detected additional gains and losses from small chromosomal regions as well as LOH events. Notably, NGS found a 16p loss, but cytogenetics detected a full chr16 loss and a 7q loss. NGS detected an 11p loss which was missed by cytogenetics. Table: Comparison of Detection by Methodologies. Conclusions: This study highlights the benefits and limitations of each method using clinical samples with hematologic disease. Cytogenetics provided a gross view of a karyotype, but lacked resolution to detect small aberrations and LOH events. NGS provided high resolution of numerical aberrations and detected LOH events, but was unable to detect some gain and loss events. In examining those missed events, < 30% abnormal cells were found in those specimens, possibly explaining the reduced sensitivity. Importantly, we found two significant discrepant chromosomal aberrations between cytogenetics and NGS. This may result from cytogenetic culture where preferential growth of cells influence the detection of a chromosome gain or loss. These findings suggest advantages in assessing chromosomal abnormalities using NGS in coordination with more traditional methods to improve diagnostic and prognostic determination to assist in treatment selection.[Table: see text]