Clinical utility of a targeted next generation sequencing panel in severe and pediatric onset Mendelian diseases

Next generation sequencing has provided great advancements in genetic diagnosis of Mendalian disorders. Simultaneous sequencing of many genes has become increasingly cheaper and faster. Recently, a number of gene panels have been established for the diagnosis of specific disease groups. The aim of this study is to evaluate the utility of an inherited disease panel in pediatric onset Mendelian diseases. Two hundred and seventeen probands and 10 carriers molecularly analyzed using a TruSight Inherited Disease^® Panel which included 552 genes responsible for pediatric onset Mendelian disorders, were enrolled in the study. The clinical phenotype, sequencing data, pretest and posttest diagnoses were evaluated. The patients in the study were classified into two groups. Group 1 (n:209) included the patients having a clinical diagnosis prior to molecular analysis. Group 2 (n:18) included the patients undiagnosed clinically prior to molecular analysis. Targeted panel provided a molecular diagnosis in 37% (84 of 227 cases) of all cases. The molecular diagnostic rate was 40.2% in patients with a specific prior clinical diagnosis. However, in patients having no primary clinical diagnosis no pathogenic variants were found. In 14 patients, a molecular diagnosis differing from the established clinical diagnosis was made. In conclusion, a targeted panel covering a high number of genes responsible for broad phenotypic spectrum can provide improved levels of diagnosis in patients with pediatric onset Mendelian diseases. A careful clinical evaluation of patients prior to the application of a next generation sequencing method leads to the best alternative approach for a conclusive molecular diagnosis.