Relationship between radiographic hilar lymphadenopathy and serologic titers for Coccidioides sp. in dogs in an endemic region.

Abstract

Hilar lymphadenopathy is a common radiographic finding in coccidioides infections. Serologic studies are used most often for the diagnosis of coccidioidomycosis in endemic areas, with IgG titers > 1:8 considered positive for infection and lower IgG titers of < 1:8 considered indicative of exposure and not necessarily related to organism presence. The objective of this study was to determine the relationship of hilar lymphadenopathy to coccidioidomycosis titers for dogs in an endemic area. A positive association between these parameters would allow treatment to be initiated before obtaining titer results. Thoracic radiographs of 131 dogs from an endemic area were reviewed for evidence of hilar lymphadenopathy. These results were compared with serology results. There was a significant association between hilar lymphadenopathy and a positive serology result (P < 0.001). With hilar lymphadenopathy as a predictor of a positive titer result, sensitivity was 28.0%, specificity was 91.5%, the positive predictive value was 43.8%; and the negative predictive value was 84.4%. There was no association between the titer result and gender, age, or weight. The radiographic finding of hilar lymphadenopathy appears to be a useful indicator of coccidioidomycosis infection in an endemic population of dogs supporting the treatment of patients for coccidioidomycosis when hilar lymphadenopathy is present and before obtaining serology results.