Evaluation of a novel monoclonal antibody‐based enzyme immunoassay for detection of Histoplasma antigen in urine of dogs

Abstract Background Commercially available, noninvasive testing options for histoplasmosis are limited outside of the United States. Objectives To describe the diagnostic performance of a novel Histoplasma antigen enzyme immunoassay (IM EIA) for the diagnosis of histoplasmosis in dogs. Animals Twenty dogs with histoplasmosis, 79 dogs without histoplasmosis, and 11 unclassified dogs providing 202 urine samples. Methods This a prospective study using stored urine samples. Samples were analyzed with the IM EIA and with the commercially available Histoplasma antigen EIA (MV EIA). Dogs were classified based on final proven diagnosis and performance of the IM EIA was described and compared with the MiraVista enzyme immunoassay (MV EIA). Results The diagnostic sensitivity (DSe), specificity (DSp), and accuracy (DAc) of the IM EIA were 70% (51%‐89%), 99% (97%‐100%), and 93% (81%‐100%), respectively. The DSe, DSp, and DAc for the MV EIA were 95% (85%‐100%), 99% (97%‐100%), and 98% (95%‐100%), respectively. The area under the receiver operator characteristic curve was significantly smaller for IM EIA (0.87) as compared with MV EIA (0.97, P = .03). This was primarily due to 6 false negative IM EIA results, 4 from dogs with disease localized to the gastrointestinal tract. The MV EIA was positive in 5/6 of these dogs. Conclusions and Clinical Importance The IM EIA might be useful for the diagnosis of disseminated histoplasmosis in dogs, but clinical usefulness will be limited in dogs with histoplasmosis localized to the GI tract.