Serial Interferon-Gamma Release Assay (IGRA) Testing to Monitor Treatment Responses in Cases of Feline Mycobacteriosis

• Main Authors: Jordan L. Mitchell, Conor O’Halloran, Paul Stanley, Kieran McDonald, Paul Burr, Danièlle A. Gunn-Moore, Jayne C. Hope
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Pathogens
• Subjects: cat; tuberculosis; mycobacteria; monitoring; interferon-gamma release assay; diagnostics
• Online Access: https://www.mdpi.com/2076-0817/10/6/657

The interferon-gamma release assay (IGRA) is used to diagnose cases of feline mycobacteriosis, but the use of serial testing to monitor treatment responses has not been evaluated in this species. From a population of cats that underwent IGRA testing for diagnostic investigation, individuals were identified with a pre- and end-of-treatment IGRA that passed control thresholds. The number of cats which reverted to negative at the end-of-treatment IGRA, changes in paired antigen-specific optical density (OD) values and differences in the pre-treatment antigen-specific OD values for those which underwent reversion were compared. Factors to explain reversion or recurrence of disease post-treatment were explored. Four of 18 cats (22%) reverted to negativity at the point of clinical resolution (<i>p</i> = 0.33), there was no difference in paired antigen-specific OD values (<i>p</i> ≥ 0.12), and cats that reverted did not have a lower baseline OD value (<i>p</i> = 0.63). No statistically significant factors were identified to predict reversion (<i>p</i> ≥ 0.08). Remaining positive at the end of treatment IGRA was not associated with recurrence of disease post-treatment (<i>p</i> = 0.34). Overall, these data suggest there is limited value in the use of the IGRA to monitor treatment responses in cats.