Lower Respiratory Tract Diseases Caused by Common Respiratory Viruses among Stem Cell Transplantation Recipients: A Single Center Experience in Korea

Hong, Kyung-Wook; Choi, Su-Mi; Lee, Dong-Gun; Cho, Sung-Yeon; Lee, Hyo-Jin; Choi, Jae-Ki; Kim, Si-Hyun; Park, Sun Hee; Choi, Jung-Hyun; Yoo, Jin-Hong; Lee, Jong-Wook

URD was defined as the detection of a CRV in upper respiratory secretions, such as nasal or throat swabs, in association with respiratory symptoms, including cough, rhinorrhea, and sore throat, and in the absence of new infiltrates on chest imaging. 9, 10 A LRD was defined as an acute respiratory illness with dyspnea, hypoxia, or pulmonary infiltrates occurring in association with the detection of a CRV in any respiratory secretions. 10 Assessment of the radiographic findings, including chest radiography and computed tomography scans, was based on the formal reading by a radiology specialist. Hospital-acquired infection was defined as symptom onset 3 or more days after hospital admission. 9 The presence of co-pathogens was defined as the isolation of pathogenic bacterial species, fungal species, or other opportunistic viruses, such as cytomegalovirus (CMV), from the respiratory specimen obtained within a month of detection of a CRV, in conjunction with consistent symptoms, and as confirmed by infectious disease specialists. 5 Proven or probable invasive fungal disease was defined according to the criteria of the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group Consensus Group in 2008. 11 A mixed CRV infection was defined by the isolation of more than two CRVs during the same episode. Mortality due to LRDs caused by CRVs was defined as death resulting from respiratory failure, with no period of complete recovery between the onset of illness and death within 30 days, and without a documented copathogen. 12 Overall mortality was defined as death from any cause within 30 days following diagnosis of CRV-LRD. An absolute lymphocyte count (ALC) of <200 cells/mm 3 blood within the 2 weeks preceding a CRV infection diagnosis was defined as lymphopenia, and an absolute neutrophil count (ANC) of <500 cells/mm 3 blood within the 2 weeks prior to a CRV infection was defined as neutropenia. 6 The dosage of corticosteroid use was classified into three groups according to the highest daily dose taken by the patient during the 2 weeks preceding a CRV infection: high-dose corticosteroid use was defined as ≥1 mg/kg/day of prednisone and its equivalent dose of corticosteroids: low-dose use was defined as ≤1 mg/kg/day of prednisone; and the third group received topical corticosteroids. 13 The grade of immunodeficiency was classified into three groups, including severe, moderate, and mild immunodeficiency. 14 Severe immunodeficiency (SID) was defined as the presence of two or more of the following: allogeneic SCT (alloSCT) within 6 months, or autologous SCT (autoSCT) within 3 months, preceding the diagnosis of a CRV infection; acute GVHD (grade ≥2); ALC <200 cells/mm 3 or ANC <500 cells/mm 3 within 2 weeks, before the diagnosis; and a pre-engraftment period or administration of immunosuppressive therapy ≤2 weeks prior to the diagnosis. Moderate immunodeficiency (MID) was defined as the presence of only one criteria of SID or two or more of the following criteria: an alloSCT within 1 year (≥6 months) or an autoSCT within 6 months (≥3 months), prior to the diagnosis of a CRV infection; ALC between 200 and 500 cells/mm 3 , or ANC between 500 and 1000 cells/mm 3 , within 2 weeks before the diagnosis; and administration of immunosuppressive drugs within 1 month prior to the diagnosis. Patients who met only one criterion of MID w