Coccidioidomycosis is associated with a broad spectrum of illness severity, ranging from asymptomatic or self-limited pulmonary
infection to life-threatening manifestations of disseminated disease. Serologic studies before the widespread availability of antifungals established current understanding of serologic kinetics and dynamics. Chart histories and
complement fixation (CF) titer trends were analyzed for 434 antifungal-treated
coccidioidomycosis patients, who were classified by three
infectious disease physicians as having either pulmonary uncomplicated
coccidioidomycosis (PUC) (n = 248), pulmonary chronic
coccidioidomycosis (PCC) (n = 64), disseminated
coccidioidomycosis (DC) not including
meningitis (n = 86), or coccidioidal
meningitis (CM) (n = 36). The median maximal CF titers were 1:4 for PUC patients, 1:24 for PCC patients, 1:128 for DC patients, and 1:32 for CM patients. Approximately 25.4% of PUC patients, 6.2% of PCC patients, 2.3% of DC patients, and 8.3% of CM patients did not develop detectable titers during the study period. Maximal titers developed a mean of 31 days (95% confidence interval [CI], 13 to 50 days) after initial serologic positivity, with no significant differences between groups. Serologic recurrence occurred in 9% of PUC patients, 36% of PCC patients, 50% of DC patients, and 52% of CM patients. Median titer improvement rates were 91 days/dilution for PUC patients, 112 days/dilution for PCC patients, 136 days/dilution for DC patients, and 146 days/dilution for CM patients. Receiver operating characteristic (ROC) analysis revealed that CF testing retains moderate classification value for disseminated
infections (area under the curve [AUC], 0.82 [95% CI, 0.78 to 0.87]) and complicated
infections (AUC, 0.82 [95% CI, 0.77 to 0.86]). A suitable cutoff value for complicated
infections is ≥1:32. Findings update serologic parameters that are relevant for clinical assessment of
coccidioidomycosis patients in the
triazole era.