In Vitro Thrombotic Tendency of Reactive Thrombocytosis in Critically Ill Patients: A Prospective Case-control Study

Abstract

It is uncertain whether reactive thrombocytosis is associated with an increased risk of thrombosis. This prospective case-control study assessed the in vitro thrombotic tendency of patients with reactive thrombocytosis. Forty-eight patients with reactive thrombocytosis, defined by platelet count >500×10 9 /l and 55 similar, randomly selected critically ill patients who did not have reactive thrombocytosis were considered. In vitro thrombotic tendency in both groups of patients was assessed using the maximal amplitude (normal range 54 to 72 mm) and alpha angle (normal range 47 to 74°) on the thromboelastograph. The associations between reactive thrombocytosis and C-reactive protein, the coagulation profile and Sequential Organ Failure Assessment score were also evaluated. Patients with reactive thrombocytosis had an associated increased in vitro thrombotic tendency (maximal amplitude 77 vs 69 mm, mean difference 8 mm, 95% confidence interval 4.9 to 10.9, P=0.001), a higher fibrinogen concentration (7.2 vs 5.8 g/l, P=0.003), and a higher incidence of infection requiring antibiotics (50 vs 27%, P=0.025) compared to patients without thrombocytosis. Platelet count had a relatively linear relationship with the maximal amplitude and the alpha angle of the thrombo-elastograph tracing (Pearson correlation coefficient: 0.53, P=0.001). In the multivariate analysis, only reactive thrombocytosis (odds ratio 5.9, 95% confidence interval 1.3 to 27.8, P=0.025) and activated partial thromboplastin time (odds ratio 0.93 per second increment, 95% confidence interval 0.87 to 0.99, P=0.016) were significantly associated with a strong in vitro thrombotic tendency. In summary, reactive thrombocytosis was associated with infection requiring antibiotics and evidence of increased in vitro thrombotic tendency in critically ill patients.

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.…”

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

“…In a prospective study of 147 splenectomy patients over a median period of 23 months, 14.3% of the patients with severe reactive thrombocytosis (> 650 × 10 9 L −1 ) without myeloproliferative diseases developed portal, mesenteric or splenic vein thrombosis compared with no VTE events among those without severe reactive thrombocytosis [23]. Our recent study also showed that reactive thrombocytosis in critically ill patients was associated with an increased in vitro thrombotic tendency and platelet counts had a relatively linear ‘dose‐related’ relationship with the strength of thrombotic tendency when measured by a thromboelastograph (Pearson’s correlation coefficient = 0.53, P < 0.001) [15]. This ‘dose‐related’ in vitro thrombotic tendency of reactive thrombosis is indeed consistent with the findings of this study – the risk of VTE is linearly related to the platelet counts when platelet counts are > 400 × 10 9 L −1 .…”

“…In this study, reactive thrombocytosis was defined as platelet count ‡ 500 · 10 9 L )1 [15]. The sample size was estimated to have 90% power if the incidence of VTE of patients without reactive thrombocytosis was 3%, incidence of reactive thrombocytosis was 20% and its associated relative risk of VTE was three.…”

“…Platelet counts were measured in 10 9 L )1 . with other prothrombotic factors or mediators such as fibrinogen [15,22], resulting in a higher risk of VTE. It is, however, well recognized that reactive thrombocytosis after splenectomy is associated with an increased risk of VTE.…”

Ten Caveats of Interpreting Correlation Coefficient in Anaesthesia and Intensive Care Research

“…First, a scatter plot is pivotal when Pearson's or Spearman's correlation coefficient is used because it allows us to visualise whether the relationship between the two variables is linear, bimodal U shape, sigmoidal or quadratic 2 . Pearson's product-moment correlation coefficient should be reserved for situations when assessment of the degree of linearity between two continuous variables is intended 3 . Other forms of regression may be more appropriate when the relationship between two variables is not linear 4 .…”