Control for Rheumatoid Factor in the Latex Test for Cryptococcosis

Abstract

The latex test has been advocated as a useful serologic test for cryptococcosis. In this test, soluble cryptococcal antigen in serum or cerebrospinal fluid agglutinates latex particles coated with rabbit anticryptococcal globulin. In a survey of 252 specimens of serum and cerebrospinal fluid, 9.5% exhibited a false positive reaction owing to rheumatoid factor. Twelve per cent of the 73 patients studied had at least one false positive specimen. A control was devised in which antiglobulin was detected by latex coated with normal rabbit globulin. With use of this control, the latex test compared very favorably with the overnight complement fixation test.