Advantages of metagenomic next-generation sequencing in the management of ANCA-associated vasculitis patients with pulmonary infections as a rule-out tool

Objective: Pulmonary infection is one of the leading causes of death in patients with ANCA-associated vasculitis (AAV). It is sometimes difficult to differentiate pulmonary infection from pulmonary involvement of vasculitis in AAV patients. Fiberoptic bronchoscopy and bronchoalveolar lavage fluid (BALF) assays are useful diagnostic methods. In addition to conventional microbiological tests (CMTs), metagenomic next-generation sequencing (mNGS) facilitates rapid and sensitive detection of various pathogens. The current study aimed to evaluate the advantages of additional BALF mNGS in the management of pulmonary infection in AAV patients. Methods: 27 patients with active AAV and suspected pulmonaryinfection whose BALF samples were tested by mNGS and CMTs and 17 active AAV patients whose BALF were tested by CMTs alone were retrospectively recruited. The results of microbiological tests and adjustments of treatment upon BALF mNGS were described. The durations of antimicrobial treatment and in-hospital mortality in patients were compared. Results: Among the 27 patients whose BALF samples were tested by mNGS, 25.9% of patients did not have any evidence of pathogenic microorganism in their BALF samples, and 55.6% of patients had polymicrobial infections, including bacteria, fungi and virus, while 40.7% of patients did not have any evidence of pathogenic microorganism in their BALF and serum samples according to CMTs tests. Patients in the BALF mNGS group received significantly shorter duration of antibacterial and total antimicrobial treatment than patients in the CMT alone group (17.3±14.7 vs. 27.9±19.0 days, P =0.044; 18.9±15.0 vs. 29.5±17.7 days, P =0.040, respectively). Patients in the BALF mNGS group had significantly lower in-hospital mortality than patients in the CMT alone group (4/27 vs. 7/17, P =0.049). Conclusion: Compared with CMT alone, additional mNGS tests may shorten the duration of antimicrobial treatment and decrease death from severe infection by providing precise and quick diagnosis of infection.