Reactive thrombocytosis and risk of subsequent venous thromboembolism: a cohort study

Abstract

Summary. Background: It is uncertain whether reactive thrombocytosis is associated with an increased risk of venous thromboembolism. This study assessed the incidence of reactive thrombocytosis, defined as platelet count ≥ 500 × 109 L−1, at intensive care unit discharge and its association with subsequent venous thromboembolism. Methods and Results: This cohort study involved linkage of routinely collected intensive care unit, laboratory, radiology and death registry data of critically ill patients admitted to the intensive care unit between January 2009 and March 2010. The census date for survival and radiologically confirmed venous thromboembolism was 31 October 2011. Of the 1446 patients who survived to intensive care unit discharge, 139 patients had reactive thrombocytosis (9.6%, 95% confidence interval [CI] 8.2–11.2%). Twenty‐nine patients developed venous thromboembolism after discharge (2%, 95% CI 1.4–2.9%; 67 per 100 person‐years, 95% CI 45–97) and the median time to develop venous thromboembolism was 25 days (interquartile range 8–148). Reactive thrombocytosis was associated with an increased risk of subsequent venous thromboembolism (hazard ratio 5.3, 95% CI 1.7–16.4), after adjusting for other covariates. Platelet counts explained about 34% of the variability in the risk of venous thromboembolism and had a relatively linear relationship with the risk of venous thromboembolism when the platelet counts were > 400 × 109 L−1. Venous thromboembolism after intensive care unit discharge was associated with an increased risk of mortality (hazard ratio 2.0, 95% CI 1.1–3.9), after adjusting for reactive thrombocytosis. Conclusions: Reactive thrombocytosis during the recovery phase of critical illness was associated with an increased risk of subsequent venous thromboembolism.

Concentration‐dependent effect of hypocalcaemia on in vitro clot strength in patients at risk of bleeding: a retrospective cohort study

“…Second, our results confirmed the increasing recognition of the importance of platelets and fibrinogen in the pathogenesis of critical bleeding, haemostasis and thrombosis (Duff et al, ; Ho et al, ; Hagemo et al, ). Our multivariate analysis results showed that fibrinogen concentrations and platelet counts certainly had a larger effect on in vitro clot strength than hypocalcaemia.…”

Platelet Count Measured Prior to Cancer Development Is a Risk Factor for Future Symptomatic Venous Thromboembolism: The Tromsø Study

“…Platelets play a central role in hemostasis and thrombosis [6], [7], but in accordance with our findings in the non-cancer cohort, the platelet count has not been associated with future risk of VTE in the general population [11]–[13]. Conversely, a significant association between reactive thrombocytosis and VTE has been confirmed in hospitalized medical patients [26], intensive care unit patients [27] and trauma patients [28], [29]. There is also growing evidence that platelet count is predictive of VTE in cancer patients.…”

Association Between Anemia and Cerebral Venous Thrombosis

“…Anemia, especially when caused by iron deficiency, can sometimes lead to thrombocytosis, which is a risk factor for venous thrombosis. 25,26 This mechanism would be in line with the fact that we observed a stronger association between CVT and microcytic anemia because iron deficiency is the most important cause of microcytic anemia. Unfortunately, thrombocytes were not measured in the MEGA study, and thus we could not examine whether the presence of thrombocytosis modified the association between anemia and CVT.…”