A Nationwide Analysis of Outcomes of Stroke in Hospitalized Patients with Essential Thrombocythemia: 2006 to 2014

Background:

Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm which is associated with an increased risk of thrombohemorrhagic complications as well as progression to myelofibrosis and frank leukemia. Patients with ET are at an elevated risk for stroke. However, studies of prevalence and outcomes of stroke in hospitalized patients with ET have been limited to case series. The median survival of patients with ET is comparable to normal population but the quality of life may be significantly altered due to the occurrence of thrombotic events in the cerebrovascular and cardiovascular systems. By conducting a retrospective analysis of nationwide data from hospitalized ET patients between the years of 2006 and 2014, we sought to identify if there are any statistically significant associations between stroke and/or in-hospital mortality with respect to patients' gender, age group, race, and comorbidities like hypertension, diabetes atrial fibrillation and chronic kidney disease.

Methods:

Data from the National Inpatient Sample was utilized to identify outcomes in hospitalized patient with ET who were admitted for stroke. The National Inpatient sample is a database maintained by the Agency for Healthcare Quality and Research. Utilizing the current procedural terminology code (CPT) for ET, outcomes of patients with ET who were hospitalized with stroke were studied for the year 2006 to 2014. Patient demographics of age, gender and race were collected and hospital characteristics of location and size were correlated to outcomes. The extent of common medical comorbidities such as hypertension, diabetes, chronic kidney disease and atrial fibrillation was studied in ET patients who died with and without stroke. Chi square test was used to determine odds ratios and multiple logistic regression was used to determine independent predictors of mortality.

Results:

Between 2006 to 2014, 552422 hospitalizations involved patients with a diagnosis of ET of which 20650 hospitalizations were due to stroke. Of these patients with stroke there was a preponderance of prevalence in females (13400 vs. 7251). The percentage of stroke in these hospitalizations varied between 3.64 to 4.29 over 15 years and mortality in these patients did not significantly change during this time period. The prevalence of stroke was highest amongst Asians and Caucasians (4.7% and 3.86%) with a statistically significant difference (p=0.0000). The age group of 80+ years and the difference in prevalence between different age groups (18-34 vs. 35-49 vs, 50-64 vs. 75-79) was statistically significant (p=0.0000) with Medicare being the insurance for most of these patients (p=0.000)). Notably, mortality was highest in the same group but was not significantly different from other age groups. Large sized hospitals were noted to have a higher proportion of ET patients with stroke compared to smaller and medium sized hospitals (p=0.0002). No difference in such proportions was noted in hospitals varying by region (Northeast vs. Midwest vs. South vs. West). Burden of medical comorbidities as measured by Charlson's comorbidity index was noted to be in the 4-6 range. Similarly, hypertension, hyperlipidemia, diabetes, atrial fibrillation, smoking status were also found to be more frequent in ET patients with stroke. A majority of ET patients with stroke were discharged to skilled nursing facilities. Multiple regression showed that female gender, atrial fibrillation, stroke, higher Charlsons comorbidity score and 80+ age were independent predictors of mortality (OR: 0.75, 1.35, 1.8, 2 to 5.7, 13.9 respectively).

Conclusions:

Patients with ET who are hospitalized with stroke have significantly worse outcomes. This study demonstrated that a statistically significant difference exists among different age groups of patients with ET and stoke who died during hospitalization when stratification is made using age groups and Charlson Score. This study may serve as an initial point to include new risk factors for further risk stratification. Early identification of patients at higher risk may reduce the incidence and decrease the morbidity of stroke in patients with ET.