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. 2019 Mar;33(2):603-610.
doi: 10.1111/jvim.15379. Epub 2018 Dec 17.

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

Lana Rothenburg  1 , Andrew S Hanzlicek  1 , Mark E Payton  2
Affiliations

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

Lana Rothenburg et al. J Vet Intern Med. 2019 Mar.

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.

Keywords: feline; fungal; histoplasmosis; mycosis.

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Conflict of interest statement

Dr. Andrew Hanzlicek has in the past, and is currently, collaborating with MiraVista Diagnostics on multiple studies relating to veterinary clinical mycology.

Figures

Figure 1
Figure 1
Box and Whisker plots demonstrating the antigen concentrations as measured by the IMMY urine Histoplasma antigen enzyme immunoassay in 35 cats with histoplasmosis at the time of diagnosis, 40 cats with alternative diagnosis at the time of diagnosis, and 19 apparently healthy cats
Figure 2
Figure 2
The diagnostic sensitivity, specificity, and accuracy of the IMMY urine Histoplasma antigen enzyme immunoassay, at different diagnostic cutoffs, for the diagnosis of histoplasmosis in 35 cats with histoplasmosis, 40 cats with an alternative diagnosis, and 19 apparently healthy cats
Figure 3
Figure 3
Receiver operating curves for the IMMY urine Histoplasma antigen enzyme immunoassay and the MiraVista urine Histoplasma antigen enzyme immunoassay for the diagnosis of histoplasmosis in 35 cats with histoplasmosis and 59 cats without histoplasmosis
See this image and copyright information in PMC

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