The serum periostin (Human Periostin/OSF-2 DuoSet kit) levels in 155 patients hospitalized for acute exacerbations of COPD were higher on admission compared to discharge (34.7 versus 25.9 ng/mL, p = 0.003), and frequent exacerbators had higher levels of serum periostin at discharge. The gene discussed is POSTN; the disease is chronic obstructive pulmonary disease.