Clinicopathological Features, Treatment Outcome, and the Cryptococcal Antigen Latex Agglutination System Titer in Feline Cryptococcosis Treated with Amphotericin B and Fluconazole.

Feline cryptococcosis is a common systemic mycosis that typically begins in the nasal cavity and can extend to the eyes, skin, and CNS. Objective monitoring during therapy remains limited. This study aimed to test whether serial serum cryptococcal antigen titers (CALAS) and a simple six-domain clinical score can track response, and to describe clinicopathologic trends during amphotericin B and fluconazole treatment. We retrospectively reviewed cases from 2014 to 2023 and analyzed a single-center cohort of 35 cats. Management used amphotericin B plus fluconazole for ~3-4 months, then fluconazole maintenance. Monthly assessments included CALAS (log2), the clinical score (0-18), and routine hematology/biochemistry; mixed-effects models tested change over time. CALAS fell (mean log2 12.00 to 6.79), total leukocytes decreased (16.85 × 109/L to 10.90 × 109/L) with a similar neutrophil decline, alanine aminotransferase remained stable, and blood urea nitrogen/creatinine increased in some cats. The clinical score improved from 3.83 to 0.68. Seven cats developed azotemia during amphotericin B; the drug was stopped, renal values normalized in three, and four remained azotemic at the last follow-up. These findings support the use of CALAS and a simple score as practical monitoring tools and underscore the need for routine renal surveillance.