Role of fungal burden in risk stratification of HIV-negative patients with Pneumocystis pneumonia: A 12-year, retrospective, observational, multicenter cohort

Objectives: This study aimed to explore the role of fungal burden in risk stratification of patients without HIV-negative patients with Pneumocystis pneumonia (PCP). Methods: This was a retrospective analysis of the characteristics associated with 30-day mortality in patients who were positive for P. jirovecii using polymerase chain reaction in bronchoalveolar lavage fluid between 2006 and 2017 in a multicenter cohort from Central Norway. The fungal burden was indicated by the cycle threshold (CT) values from semiquantitative real-time polymerase chain reaction targeting the β-tubulin gene. Results: We included 170 patients with proven or probable PCP. The all-cause 30-day mortality was 18.2%. After adjusting for host characteristics and premorbid corticosteroid use, a higher fungal burden was associated with a higher risk of dying: adjusted odds ratio 1.42 (95% confidence interval 0.48-4.25) for a CT value 31-36, increasing to odds ratio 5.43 (95% confidence interval 1.48-19.9) for a CT value ≤30 compared with patients with a CT value ≥37. The Charlson comorbidity index (CCI) improved the risk stratification: patients with a CT value ≥37 and CCI ≤2 had a 9% mortality risk compared with 70% among those with a CT value ≤30 and CCI ≥6. Comorbid cardiovascular disease, solid tumors, immunological disorders, premorbid corticosteroids, hypoxemia, abnormal leukocyte counts, low serum albumin, and C-reactive protein ≥100 were also independently associated with 30-day mortality. The sensitivity analyses did not suggest selection bias. Conclusion: Fungal burden may improve the risk stratification of patients without HIV-negative patients with PCP.