Parainfluenza Virus Lower Respiratory Tract Disease After Hematopoietic Cell Transplant: Viral Detection in the Lung Predicts Outcome

Background. Parainfluenza virus (PIV) commonly infects patients following hematopoietic cell transplantation (HCT), frequently causing lower respiratory tract disease (LRTD). The definition of LRTD significantly differs among studies evaluating the impact of PIV after HCT. Methods. We retrospectively evaluated 544 HCT recipients with laboratory-confirmed PIV and classified LRTD into 3 groups: possible (PIV detection in upper respiratory tract with new pulmonary infiltrates with/without LRTD symptoms), probable (PIV detection in lung with LRTD symptoms without new pulmonary infiltrates), and proven (PIV detection in lung with new pulmonary infiltrates with/without LRTD symptoms). Results. Probabilities of 90-day survival after LRTD were 87%, 58%, and 45% in possible, probable, and proven cases, respectively. Patients with probable and proven LRTD had significantly worse survival than those with upper respiratory tract infection (probable: hazard ratio [HR], 5.87 [P < .001]; proven: HR, 9.23 [P < .001]), whereas possible LRTD did not (HR, 1.49 [P = .27]). Among proven/probable cases, oxygen requirement at diagnosis, low monocyte counts, and high-dose steroid use (> 2 mg/kg/day) were associated with high mortality in multivariable analysis. Conclusions. PIV LRTD with viral detection in lungs (proven/probable LRTD) was associated with worse outcomes than was PIV LRTD with viral detection in upper respiratory samples alone (possible LRTD). This new classification should impact clinical trial design and permit comparability of results among centers.