Determination of the sensitivity and specificity of immunodiffusion (ID) and complement fixation (CF), using fungal antigens produced in the mycology service

Abstract

In the present work of immunodiagnosis of mycosis, the Complement Fixation (CF) technique was implemented and standardized; with the antigens and antiserums of Histoplasma capsulatum and Coccidioides immitis produced locally to improve the diagnosis of infections caused by the mentioned fungi, and it was compared with the Agarose Gel Immunodiffusion (ID) test, already established in our laboratory. The Complement Fixation test was performed in two phases: 1) Titration of the reagents and II) Diagnostic test. Thus, the first is basic for the second. The sera of 83 patients with different conditions were compared (apparently healthy patients from endemic areas of the aforementioned fungi, patients with confirmed tuberculosis and the third group of patients with confirmed deep mycoses produced by C. immitis H. cagsulatum). One patient tested positive for histoplasmin in both tests, ID and FC. The same occurred with coccidioidin, with only one patient testing positive. Both patients had previously been diagnosed with ID. These results were observed despite having used between 80 - 85% of the sera contaminated with bacteria, which caused false positives in FC, but not with ID. The experience acquired in the implementation of FC with our own antigens and antiserums allowed us to establish that the quality and potency of the same in their raw form, work adequately in screening tests such as ID, but in the case of FC, because it is quantitative and of greater sensitivity, it is necessary to improve its potency and achieve its purification. That FC, in our laboratory works well with phenolic hemolysins and it is recommended to use the commercial complement, since we tried to obtain fresh complement from guinea pig serum, but it turned out to be very labile, with low titers and in small quantities.