Long-standing thrombocytosis and thrombotic events preceding recognition of polycythaemia vera: a single-centre retrospective study.

Abstract

Background: Patients with polycythaemia vera are at a higher risk for thrombotic events, which may occur at any time before diagnosis, at diagnosis or later during the disease. Besides an increased haematocrit, thrombocytosis may be an early marker of polycythaemia vera. Our study aimed to analyse the frequency of thromboembolic events and the presence of thrombocytosis/erythrocytosis preceding the diagnosis of polycythaemia vera.

Methods: This monocentric, retrospective study included patients diagnosed with polycythaemia vera, aged 18 years or over, seen at our institution between January 2008 and December 2018. Baseline demographics, polycythaemia vera diagnosis information, comorbidities, presence and type of thromboembolic events, and blood counts before thromboembolic events and polycythaemia vera diagnosis were analysed.

Results: A total of 79 eligible patients were included. There was a slight male predominance (57%) with a median age at polycythaemia vera diagnosis of 69 years. Fifty-two patients (66%) had a thromboembolic event (24 before or concomitant with polycythaemia vera diagnosis, 11 after polycythaemia vera diagnosis and 17 both before and after polycythaemia vera diagnosis). Overall, 40 patients experienced arterial thrombotic events and 31 experienced venous thrombotic events. For the 41 patients with thromboembolic events before or concomitant to the polycythaemia vera diagnosis, the median platelet count at the time of the thromboembolic event was 365×109/l before and 479×109/l at polycythaemia vera diagnosis; the median leukocyte count was 11.2×109/l and 11.5×109/l, respectively; haemoglobin (haematocrit) level was 168 g/l (50%) and 179 g/l (53%), respectively. We had access to 90 blood counts performed before polycythaemia vera diagnosis in 17 patients with a thromboembolic event prior or concomitant with the polycythaemia vera diagnosis. For these patients, the median time from the first blood count showing platelets >350×109/l or >450×109/l to the diagnosis of polycythaemia vera was 36 months and 24 months, respectively. Four patients had a thromboembolic event prior to polycythaemia vera diagnosis with a normal platelet count. In these four patients, the median delay between the thromboembolic event and the polycythaemia vera diagnosis was 32 months. For the remaining 13 patients, the median time from the first blood count with platelets >350×109/l or >450×109/l and the thromboembolic event was 46 months and 10 months, respectively. The median time from the earliest available blood count showing Hb >16.5 g/dl (Hct >49%) for men or Hb >16.0 g/dl (Hct >48%) for women to the diagnosis of polycythaemia vera was 25 months and 24 months, respectively, and to the thromboembolic event was 12 months and 13 months, respectively.

Conclusion: Our study shows that both thrombocytosis and/or erythrocytosis are frequently present months and even years before the diagnosis of polycythaemia vera. In addition, the occurrence of a thrombotic event may be the earliest indicator of polycythaemia vera, particularly with thrombocytosis >350×109/l. The presence of thrombocytosis and/or erythrocytosis, even moderate, in the absence of a secondary cause, should evoke suspicion of a myeloproliferative neoplasia, including polycythaemia vera.