P1665: WHOLE-BLOOD ROTATIONAL THROMBOELASTOMETRY (ROTEM) AS A DIAGNOSTIC TOOL IN PATIENTS WITH BLEEDING OF UNKNOWN CAUSE (BUC) - D. Mehic; B. Jilma; C. Schörgenhofer; M. Colling; C. Ay; I. Pabinger; J. Gebhart (HemaSphere, 2022)