Summary
It is uncertain whether thrombocytosis without underlying myeloproliferative diseases
is associated with an increased risk of acute pulmonary embolism (PE). We investigated
the relationship between thrombocytosis and risk of symptomatic acute PE, and whether
Pulmonary Embolism Severity Index (PESI) was reliable in predicting mortality of acute
PE. This multicentre registry study involved a total of 609,367 critically ill patients
admitted to 160 intensive care units (ICUs) in Australia or New Zealand between 2006
and 2011. Forward stepwise logistic regression was used to assess the relationship
between risk of acute PE and platelet counts on intensive care unit (ICU) admission.
Acute PE (n=3387) accounted for 0.9% of all emergency ICU admissions. Over 20% of
all PE required mechanical ventilation, 4.2% had cardiac arrest, and the mortality
was high (14.8%). Thrombocytosis, defined by a platelet count >500×109 per litre, occurred in 2.1% of the patients and was more common in patients with
acute PE than other diagnoses (3.4 vs. 2.0%). The platelet counts explained about
4.5% of the variability and had a linear relationship with the risk of acute PE (odds
ratio 1.19 per 100×109 per litre increment in platelet count, 95% confidence interval 1.06–1.34), after
adjusting for other covariates. The PESI had a reasonable discriminative ability (area
under receiver-operating-characteristic curve = 0.78) and calibration to predict mortality
across a wide range of severity of acute PE. In summary, thrombocytosis was associated
with an increased risk of symptomatic acute PE. PESI was useful in predicting mortality
across a wide range of severity of acute PE.
Keywords
Embolism - epidemiology - platelets - PESI - prediction - risk factors
