Osteopontin (OPN) improves risk stratification in pulmonary hypertension (PH) - Rosenberg, Mark; Meyer, Franz Joachim; Grünig, Ekkehard; Schuster, Tibor; Lutz, Matthias; Loßnitzer, Dirk; Wipplinger, Rita; Katus, Hugo; Frey, Norbert (International journal of cardiology, 2012)