Real-World Impact of Deep Targeted Sequencing on Erythrocytosis and Thrombocytosis Diagnosis: A Reference Centre Experience.

Despite advances in diagnosis of erythrocytosis and thrombocytosis due to driver mutation testing, many cases remain classified as "idiopathic". This can be explained by the absence of an evident secondary cause, inconclusive bone marrow biopsy or neglection of family history. Analysis of a broad panel of genes through next-generation sequencing (NGS) could improve diagnostic work-up identifying underlying genetic causes. We reviewed the results of NGS performed in our laboratory and its diagnostic impact on 117 patients with unexplained erythrocytosis and 58 with unexplained thrombocytosis; six patients (5.1%) were diagnosed with polycythaemia vera (PV) and 8 (6.8%) with familial erythrocytosis after NGS testing. Low EPO and a family history seemed to predict a positive result, respectively. However, a greater percentage of patients were ultimately diagnosed with secondary erythrocytosis (36%), remained as idiopathic (28.2%) or were self-limited (15%). The yield of NGS was shown to be slightly higher in patients with thrombocytosis, as 15 (25.9%) were diagnosed with essential thrombocythemia (ET) or familial thrombocytosis after variant detection; previous research has shown similar results, but most of them carried out NGS retrospectively, while the present study exhibits the performance of this test in a real-world setting. Overall, the low rate of variant detection and its poor impact on diagnostic work-up highlights the need for a thorough screening prior to NGS, in order to improve its yield.