Respiratory syncytial virus in hematopoietic cell transplant recipients and patients with hematologic malignancies

Khawaja, Fareed; Chemaly, Roy F.

The most significant complication of RSV infection in HM patients and HCT recipients is progression to LRTI, which is associated with a higher mortality rate. 5, 20, 22, 24, 25, [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] Many risk factors for progression have been identified in the hopes that target populations that could benefit from early therapy could be identified. These risk factors primarily consist of host factors, as previous studies on RSV serotypes A and B found no differences in outcomes. 35, 52 To assist with the identification of HCT recipients who are at risk of progression to LRTI and a fatal outcome, an Immunodeficiency Scoring Index (ISI) for RSV was developed based on a combination of multiple host risk factors, 53 which means it is applicable to other respiratory viruses. Six factors were included in the scoring index: neutropenia of less than 500 neutrophils/mL, lymphopenia of less than 200 lymphocytes/mL, age greater than 40 years, graft-versus-host disease, steroid use, myeloablative chemotherapy, and time from HCT. 53 On the basis of the total score, the ISI stratifies HCT recipients with RSV URTI into low-risk (score of 0-2), medium-risk (score of 3-6), and high-risk (score of 7-12) categories. 53 Other risk factors that were identified in other studies and were not included in the ISI were smoking status, 54 hypoxia, 28 nosocomial infection, 28,37 matched unrelated donor/mismatched donor status, 25, 42, 55 prior autologous HCT, and stem cell source 25, 28 (Table 2 ). The ISI for RSV has been validated by other authors 12, 56 (Table 3) . Wang et al. found that allogenic HCT recipients with high ISI scores experienced progression to pneumonia after being diagnosed with RSV, influenza, coronavirus, or adenovirus. 12 There is currently no predictive scoring index for the progression of respiratory viruses in patients with leukemia, lymphoma, or multiple myeloma. On the other hand, there are well-described risk factors that are associated with progression to LRTI in HM patients; these include lymphopenia and neutropenia, 4, 28, 37, 54, 55, 57 which are generally defined as ≤200 lymphocytes/mL 37, 54, 57 and ≤500 neutrophils/mL, respectively .In multiple retrospective analyses of HCT recipients, lymphocytopenia 4,37,54,57 and neutropenia 4, 37, 54, 57 at the time of the diagnosis of RSV were independent predictors of progression to LRTI.