[Diagnostic workup in front of an adult thrombocytosis].

During a blood test, the discovery of thrombocytosis is a frequent phenomenon with multiple origins. False thrombocytosis linked to analytical interferences is rare but must be eliminated before confirming the anomaly. The reaction origin, often very easily demonstrated by the context and/or the presence of a biological inflammatory syndrome, is the most frequent. More rarely, the diagnosis is oriented towards a clonal hematological pathology not limited to essential thrombocythemia. Currently, many biological tools, which have largely contributed to the recommendations of the latest WHO classification of chronic myeloid neoplasms, are available to classify these pathologies as precisely as possible, allowing optimal management.