Birgitta Versluijs

65 HRCT after hematopoietic cell transplantation Introduction Hematopoietic cell transplantation is a potentially curative therapy for many patients with a variety of malignant and nonmalignant disorders. 1 Unfortunately, hematopoietic cell transplantation can be complicated by life-threatening infectious and noninfectious pulmonary complications. 2 Infectious complications are caused by viruses, fungi, and bacteria. Noninfectious complications include toxicity of treatment (for instance, fluid overload, capillary leakage, and late fibrosis due to chemotherapy) and alloimmune me- diated lung syndromes. The management of these complications is critically dependent on the most probable diagnosis; which is based on patient characteristics; clinical pre- sentation; time of onset after hematopoietic cell trans-plantation; and additional tests including laboratory tests, cultures, and imaging workup. Early after hematopoietic cell transplantation, clinical symptoms largely overlap, and differentiating alloimmune lung syndromes (allo-LS) from non-alloimmune lung syndromes (nonallo-LS) is therefore difficult. This distinction is crucial because the treatment of these complications is op- posite: either increasing or decreasing immunosuppressive therapy. Therefore, sensi- tive early diagnosis strategies will definitely impact the treatment response of these life- threatening pulmonary complications and subsequent survival after hematopoietic cell transplantation. High-resolution CT (HRCT) findings for various pulmonary complications after hema- topoietic cell transplantation have been described, 3–16 and much overlap is present in the prevalence of individual findings. Whether HRCT can differentiate between allo-LS and nonallo-LS is not well known. It remains challenging to provide useful additional diag- nostic information from HRCT in hematopoietic cell transplantation recipients who pre- sent with respiratory symptoms. We hypothesize that it is not the presence of a specific HRCT finding but rather the combination and severity of HRCT abnormalities described in a semi-quantitative alloimmune score (allo-score) that might be helpful in making a diagnosis of allo-LS. The aims of this study were to develop an HRCT score to predict allo-LS in patients with respiratory complications after hematopoietic cell transplanta- tion and to assess its interobserver reliability. Materials and methods Study population This was a retrospective study of all chest HRCT in pediatric hematopoietic cell trans- plant recipients between January 2004 and September 2012. The studies were perfor- med because of significant respiratory symptoms after hematopoietic cell transplanta- tion. This study focuses on patients with respiratory symptoms early (< 100 days) after 4