ST2 in emergency department patients with noncardiac dyspnea

Objectives: Serum 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. Methods: This 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 > 500 pg/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. Results: Of 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 180 days, 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 227 ng/mL in patients who died versus 32 ng/mL in those who survived (difference = 195 ng/mL, 95% confidence interval [CI] = 48 to 342 ng/mL, p = 0.006). Median ST2 level was 59 ng/mL in readmitted patients versus 31 ng/mL in nonreadmitted patients (difference = 28 ng/mL, 95% CI = -3 to 60 ng/mL, p = 0.036). Median ST2 levels were 41 ng/mL in patients with return ED visits versus 31 ng/mL in those without return visits (difference = 10 ng/mL, 95% CI = -10 to 20 ng/mL, p = 0.23). Conclusions: Patients with noncardiac dyspnea who died or required readmission to the hospital within 180 days 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.