Serologic testing for IgM and IgG antibodies with CF isregularly used in order to diagnose infections due to Coccidioidesand help guide therapy.4,18 One small study, analyzing patients with HIV and disseminatedC immitis, showed consistently negative CF titers in 25% of patients.18 Another retrospective study documents initial negative serology in 17% of HIVpatients with confirmed Coccidioides. Here, CFTR is linked to infection.