Specificity of the latex-cryptococcal antigen test.

Abstract

Three per cent of 618 serum specimens and 9% of 220 cerebrospinal fluid (CSF) specimens submitted from patients suspected of having fungal infections were positive in the latex–cryptococcal antigen test (LCAT). Fifteen per cent of the positive results in CSF and 85% of those in serum were nonspecific reactions. Latex particles coated with rabbit globulin were agglutinated by every serum and CSF specimen producing a nonspecific LCAT, but the latex-rabbit globulin test reagent did not agglutinate in any of the serum or CSF specimens from patients with proved cryptococcosis. Eighty-seven per cent of sera containing rheumatoid factor, from patients with rheumatoid arthritis, agglutinated the LCAT reagent; 60% of the same sera agglutinated the latex-rabbit globulin test reagent. Performing the latex-rabbit globulin test and rheumatoid factor tests in parallel with the LCAT should indicate virtually all nonspecific agglutinations. Three of 29 serum specimens from patients with other proved mycotic and actinomycotic infections agglutinated the LCAT reagent, but all of these appeared to be nonspecific reactions and were detected by the latex- rabbit globulin test reagent. None of 50 serum specimens from healthy blood bank donors agglutinated the LCAT reagent.