Clinical and serologic variables associated with dissemination and seasonal presentation in dogs with newly diagnosed coccidioidomycosis
Lauren Chittick, Jared A Jaffey, Andrew S Hanzlicek, Rachael Kreisler, Laura H Rayhel, Jennifer Balaban, Cody Alcott, Christopher Adams, Aubrey G GouldAbstract
Background
Disseminated coccidioidomycosis in dogs is associated with substantial morbidity, yet distinguishing pulmonary from disseminated disease can be clinically challenging. Antibody serology might assist in predicting dissemination, but its performance across disease sites requires clarification.
Hypothesis/Objectives
To identify clinical and serologic variables associated with disseminated coccidioidomycosis and to evaluate differences in antibody magnitude among common sites of infection.
Animals
Two hundred fourteen client-owned dogs with newly diagnosed coccidioidomycosis.
Methods
Retrospective study. Anti-Coccidioides spp. immunoglobulin (Ig)G was measured by enzyme immunoassay (EIA) and agar gel immunodiffusion (AGID) at a reference laboratory.
Results
Disease was classified as pulmonary in 148/214 (69%) and disseminated in 66/214 (31%). Higher EIA IgG concentration and AGID IgG titer were independently associated with dissemination. Enzyme immunoassay discriminated disseminated from pulmonary disease well (area under the curve [AUC]: 0.81; 95% confidence interval [CI], 0.74-0.87), estimate likely representing an upper bound because serology contributed to case classification. Agar gel immunodiffusion performance was not statistically distinguishable (AUC: 0.74; 95% CI, 0.67-0.82; P = .65). Exploratory cutpoints included an EIA IgG threshold of 37 enzyme immunoassay units (sensitivity 86%, specificity 63%) and an AGID IgG threshold of ≥1:32 (sensitivity 48%, specificity 86%). Pulmonary diagnoses were least common in spring and peaked in late fall and winter.
Conclusions and clinical importance
Coccidioidal IgG serology might provide clinically useful adjunctive information when assessing dogs for disseminated coccidioidomycosis. However, overlap in serologic results between disease phenotypes precludes the use of serology alone to determine disease extent. Serologic results should therefore be interpreted alongside clinical findings and appropriate diagnostic evaluation.