A LATEX CRYPTOCOCCAL ANTIGEN AGGLUTINATION-TEST FOR DIAGNOSIS AND MONITORING OF THERAPY FOR CRYPTOCOCCOSIS

A latex cryptococcal antigen agglutination test (LCAT) was performed o n sera obtained during the first 14 days of treatment from 58 animals (46 cats, 9 dogs, 2 koalas and 1 long billed corella) with cryptococco sis. The same commercial kit was used for all samples, and most serum samples were treated with pronase before testing. Sera from all 58 cas es tested positive with the qualitative LCAT protocol (using undiluted sera), while sera from all 26 cats without cryptococcosis rested nega tive. Titres determined using the quantitative protocol ranged from 1 to greater than or equal to 131 072 (median titre between 2048 and 409 6), with 57 of 58 cases (including all 8 animals that presented for ne urological signs) having tires greater than or equal to 2 and thus con sidered positive according to the manufacturer's recommendations. The LCAT titre was positively correlated with disease severity (r = 0.4169 ; P = 0.0011), and patients with disseminated skin and/or lymph node i nvolvement had significantly higher titres than those that did not (P = 0.0157). The presence of neurological signs, the species of the pati ent, concurrent viral disease (in cats) and the biotype of the isolate had no significant association with the LCAT titre, Cats that died of active cryptococcosis despite treatment did not have significantly hi gher titres (P = 0.3010) than those that responded to treatment. Seque ntial LCAT determinations obtained in 37 patients during treatment pro vided a useful quantitative indication of clinical progress, although the decline in titre lagged somewhat behind clinical improvement, Gene rally, the antigen titre declined by 2 to 4 fold per month during succ essful therapy. Although there are insufficent data to make unequivoca l recommendations, we suggest that either antifungal therapy be contin ued until the LCAT titre declines to less than 1, or therapy be discon tinued after a 32 fold or greater reduction in titre, with periodic mo nitoring of the serum antigen titre. Treatment of serum samples with p ronase substantially increased the sensitivity of the LCAT.