A monoclonal antibody‐based urine Histoplasma antigen enzyme immunoassay (IMMY®) for the diagnosis of histoplasmosis in cats

Abstract

Background An in‐house Histoplasma urine antigen test for cats might be desirable in certain situations. Objective To validate and compare the diagnostic performance of a monoclonal antibody‐based IMMY urine Histoplasma antigen enzyme immunoassay (IMMY EIA) to the commercially available urine Histoplasma antigen enzyme immunoassay (MiraVista Diagnostics, MV EIA). Animals One hundred ninety‐three urine samples from 105 client‐owned and purpose‐bred research cats. Methods Cats were classified as Histoplasma positive or negative based on diagnostic investigation. The IMMY EIA and MV EIA were performed on all urine samples. Correlation and agreement between the assays were determined. Diagnostic performance was determined and compared between assays. Results The IMMY EIA, with a 0.25 ng/mL diagnostic cutoff, provided a diagnostic sensitivity (DSe), diagnostic specificity (DSp), and diagnostic accuracy (DAc) of 89% (95% confidence interval [CI]; 73%‐97%), 80% (67%‐89%), and 83% (74%‐90%), respectively. The IMMY EIA, with a 1.1 ng/mL diagnostic cutoff, provided a DSe, DSp, and DAc of 77% (95% CI 60%‐90%), 97% (88%‐100%), and 89% (81%‐95%), respectively. The MV EIA provided a DSe, DSp, and DAc of 94% (95% CI 81%‐99%), 97% (89%‐100%), and 96% (90%‐99%), respectively. Moderate overall agreement was found between MV EIA and IMMY EIA using the 0.25 ng/mL cut‐off (к = 0.44; 95% CI 0.31‐0.57) and the 1.1 ng/mL cut‐off (к = 0.43, 95% CI, 0.31‐0.56). Conclusions and Clinical Importance The IMMY EIA might be useful as a diagnostic test for histoplasmosis in cats. Further modifications of the IMMY EIA are required to achieve the diagnostic performance of the MV EIA.

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

“…Repeatability was adequate as the intra‐assay %CV and interassay %CV was below the OIE recommended maximum of 15% 25 . The LLOQ of 0.35 ng/mL was similar, but slightly lower than the 0.5 ng/mL LLOQ reported in humans and cats 12,26 . Due to how it was calculated, it is possible our study underestimated the LLOQ for the IM EIA.…”

“…25 The LLOQ of 0.35 ng/mL was similar, but slightly lower than the 0.5 ng/mL LLOQ reported in humans and cats. 12,26 Due to how it was calculated, it is possible our study underestimated the LLOQ for the IM EIA. also utilized samples stored for years in some cases.…”

“…Testing was performed with commercially available monoclonalantibody agent specific reagents (IMMY) with slight modification from that previously described in humans and cats. 12,13 In short, an…”

Timely Diagnosis of Histoplasmosis in Non-endemic Countries: A Laboratory Challenge

“…Histoplasma antigen detection in body fluids is currently considered the most sensitive and quickest technique to diagnose this infection (Azar and Hage, 2017). It is particularly useful in progressive disseminated forms, and it has proven its applicability to infected animals that may act as potential reservoirs for humans (Cunningham et al, 2015;Rothenburg et al, 2019). Combined detection in serum and urine seem to provide the best diagnostic performance, with some differences in the diagnostic yield between FDA cleared tests (Theel et al, 2013;Fandiño-Devia et al, 2016;Azar and Hage, 2017;Torres-González et al, 2018).…”

“…Education has proven to be an essential tool to increase the recognition of cases in endemic resource-constrained settings (Caceres et al, 2015), and also, it may be a future strategy to implement in non-endemic areas. Other pillars of utmost importance to effectively fight against histoplasmosis should be to consider it a notifiable infection, to quantify the real extent of the problem (Bongomin et al, 2019b;Staffolani et al, 2020), and to put into practice the use of rapid and reliable tools to detect and control potential environmental and animal sources of human infection (Cunningham et al, 2015;Gómez et al, 2018Gómez et al, , 2019Rothenburg et al, 2019).…”