Serum cryptococcal antigen gradient detection for monitoring the efficacy and medical guidance of the treatment of pulmonary cryptococcosis: a case report.

BACKGROUND: The duration of drug maintenance therapy for pulmonary cryptococcosis (PC) has been controversial, and good monitoring methods for drug efficacy are lacking. CASE PRESENTATION: An immunocompetent patient diagnosed with PC was admitted in 2020. He had no history of immune deficiency but reported being extremely tired at the time and possibly exposed to pigeon dropping. The diagnosis was confirmed through serum cryptococcal antigen (CrAg) testing and pulmonary high-resolution computed tomography (HRCT) imaging, and the patient received oral fluconazole therapy immediately. During the treatment period, the serum was serially diluted to monitor CrAg changes via simple colloidal gold test strip detection to assess disease progression and therapeutic efficacy. After 4 months of oral fluconazole therapy, the serum CrAg was changed to negative, and the drug was discontinued after one month of maintenance therapy. Four years of follow-up revealed that the patient had recovered. CONCLUSION: This case proposes a simple and convenient method for the diagnosis and management of PC, particularly the use of serial dilutions of serum to track CrAg for the possibility of monitoring the efficacy of therapy and treatment duration. CLINICAL TRIAL NUMBER: Not applicable.