Letter to the Editor on: "Nosocomial Respiratory Virus Infections in Hematologic Malignancies: Risk Factors for Progression to Lower Respiratory Tract Infection".

This Correspondence responds to Oh and colleagues' study on nosocomial respiratory virus infections in hematologic malignancies and risk factors for progression to lower respiratory tract infection. We raise three methodological concerns: (1) the landmark analysis used to evaluate URTI-stage ribavirin therapy excludes patients who progressed or died before landmark time points, introducing selection bias by conditioning on a collider; (2) antiviral therapy analyses are severely underpowered (only 15 PIV and 9 RSV treated patients), with wide confidence intervals precluding definitive conclusions and substantial Type II error risk; and (3) combining glucocorticoid exposures from different indications (short-course pulse vs. prolonged therapy) may mask heterogeneous effects on immune function and viral progression. We commend the authors' risk stratification framework while urging cautious interpretation of antiviral efficacy data and recommending future prospective studies with adequate sample sizes and refined corticosteroid characterization.