Abstract
Lung transplant recipients (LTRs) are susceptible to opportunistic infections, including invasive nocardiosis (IN) and invasive mucormycosis (IM). Polymerase chain reaction (PCR) testing of bronchoalveolar lavage (BAL) fluid offers rapid pathogen detection, but its clinical utility in LTRs is understudied.
We conducted a single-center, retrospective cohort study of adult LTRs who underwent BAL PCR testing for Nocardia spp. or Mucorales spp. (January 2020-December 2024); samples from both surveillance and "for-cause" bronchoscopies were included. The primary outcome was development of clinical infection within 6 months of PCR testing. We calculated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Patient-level analyses were performed for PCR-positive LTRs. Fisher's exact and Mann-Whitney U tests were used for calculating p-values.
Of 4279 Nocardia and 3588 Mucorales BAL PCR tests, 1.7% and 1.4% of samples were positive, respectively. Sensitivity, specificity, PPV, and NPV were 92.3%, 98.6%, 16.7%, and 99.98% for Nocardia and 76.2%, 99.1%, 32.0%, and 99.9% for Mucorales. Abnormal chest CT findings and for-cause bronchoscopy increased the PPV to 34.3% for Nocardia and 68.2% for Mucorales. At the patient level, both IN and IM were associated with abnormal imaging and for-cause bronchoscopy.
BAL PCR testing for Nocardia and Mucorales demonstrates excellent specificity and NPV but low PPV. Meaningful PPV was observed primarily in patients undergoing for-cause bronchoscopy with radiographic abnormalities. PCR results can be useful adjuncts in appropriate clinical settings, but have little utility among LTRs with normal imaging undergoing surveillance testing.