ST2 in Emergency Department Patients With Noncardiac Dyspnea

ObjectivesSerum levels of soluble ST2, a member of the interleukin-1 receptor family, predict mortality in emergency department (ED) patients with dyspnea secondary to acute heart failure and acute coronary syndrome. Elevated levels of ST2 have also been described in pulmonary disease, but it is unclear if these are associated with adverse outcomes. The hypothesis for this study was that elevated ST2 levels would be associated with 180-day mortality and 180-day return ED visits or hospital readmission in patients presenting to the ED with noncardiac causes of dyspnea. MethodsThis prospective observational cohort study enrolled a convenience sample of patients presenting to a single academic tertiary care ED with a chief complaint of dyspnea. Exclusion criteria included dyspnea due to chest wall trauma, airway obstruction, and known cardiac etiology (new onset heart failure, prior heart failure with current brain natriuretic peptide >500pg/mL, presumed ischemic chest pain, elevated troponin, electrocardiogram changes indicating myocardial infarction or ischemia, heart transplant). ST2 levels were measured at ED presentation and compared between those with and without adverse outcomes. Staff were blinded to ST2 levels. Differences between groups were assessed using the Mann-Whitney U test. ResultsOf the 82 patients enrolled, 45 (55%) were female, 48 (59%) were African American, and 34 (42%) were hospitalized. The most frequent ED or hospital diagnosis was chronic obstructive pulmonary disease (COPD) or asthma, in 29 (35%) patients. At 180days, 36 of 81 patients (44%) had return ED visits, 21 of 81 patients (26%) were readmitted, and five of 82 patients (6%) were deceased. Median ST2 level was 227ng/mL in patients who died versus 32ng/mL in those who survived (difference= 195ng/mL, 95% confidence interval [CI]=48 to 342ng/mL, p=0.006). Median ST2 level was 59ng/mL in readmitted patients versus 31ng/mL in nonreadmitted patients (difference= 28ng/mL, 95% CI=-3 to 60ng/mL, p=0.036). Median ST2 levels were 41ng/mL in patients with return ED visits versus 31ng/mL in those without return visits (difference= 10ng/mL, 95% CI=-10 to 20ng/mL, p=0.23). ConclusionsPatients with noncardiac dyspnea who died or required readmission to the hospital within 180days had higher levels of ST2 compared with nonadmitted survivors. Further research into ST2 as a prognostic tool in pathologic processes not involving the heart, such as pulmonary disease, is warranted.