Value of the concomitant use of complement fixation and immunodiffusion tests in the diagnosis of coccidioidomycosis.

Complement fixation titers of 1:2 and 1:4 with coccidioidin are not always of diagnostic significance. The concurrent use of the complement fixation and immunodiffusion tests is an effective means for specific serologic diagnosis of coccidioidomycosis in patients with low levels of complement-fixing antibodies. In routine testing, it is recommended that only sera that are negative for complement-fixing antibodies at 1:8 but positive in the immunodiffusion test with coccidioidin be selected for titration at the 1:2 and 1:4 levels.