Pulmonary cryptococcosis in solid organ transplant recipients: clinical relevance of serum cryptococcal antigen.

Background: The role of serum cryptococcal antigen in the diagnosis and determinants of antigen positivity in solid organ transplant (SOT) recipients with pulmonary cryptococcosis has not been fully defined.

Methods: We conducted a prospective, multicenter study of SOT recipients with pulmonary cryptococcosis during 1999-2006.

Results: Forty (83%) of 48 patients with pulmonary cryptococcosis tested positive for cryptococcal antigen. Patients with concomitant extrapulmonary disease were more likely to have a positive antigen test result (P=.018), and antigen titers were higher in patients with extrapulmonary disease (P=.003) or fungemia (P=.045). Patients with single nodules were less likely to have a positive antigen test result than were those with all other radiographic presentations (P=.053). Among patients with isolated pulmonary cryptococcosis, lung transplant recipients were less likely to have positive cryptococcal antigen test results than were recipients of other types of SOT (P=.003). In all, 38% of the patients were asymptomatic or had pulmonary cryptococcosis detected as an incidental finding. Nodular densities or mass lesions were more likely to present as asymptomatic or incidentally detected pulmonary cryptococcosis than as pleural effusions and infiltrates (P=.008).

Conclusions: A positive serum cryptococcal antigen test result in SOT recipients with pulmonary cryptococcosis appears to reflect extrapulmonary or more advanced radiographic disease.