Clinical performance of a commercially available thymidine kinase 1 assay for diagnosis of lymphoma in 42 hospitalized horses (2017-2020).

BACKGROUND

Antemortem definitive diagnosis of lymphoma in horses is often difficult. Thymidine kinase 1 (TK1) assay is a potentially useful biomarker for lymphoma in horses.

HYPOTHESIS/

OBJECTIVES

To report the clinical performance of a commercially available TK1 assay for diagnosis of lymphoma in horses. We hypothesized that there would be no association between serum TK1 activity and a diagnosis of lymphoma in horses.

ANIMALS: Forty-two hospitalized horses, 14 with a definitive diagnosis of lymphoma, 4 with other neoplasia, and 24 with inflammatory disease.

METHODS

Retrospective medical record review, groups were compared via Kruskal-Wallis and Mann-Whitney tests, and logistic regression was performed.

RESULTS

Median (range) TK1 was 3 U/L (0.4-17.7 U/L) in horses with lymphoma and 3.9 U/L (0.8-94 U/L) in horses without lymphoma (P = .59). There was no significant difference in total protein between horses with and without lymphoma (6.6 g/dL [5.5-8.3 g/dL] vs 6.6 g/dL [4.7-10.4 g/dL]; P = .83). There was no significant difference in fibrinogen between horses with and without lymphoma (447 [100-1364] mg/dL vs 433 [291-2004] mg/dL; P = .47). On logistic regression, serum TK1 activity was not associated with a diagnosis of lymphoma (odds ratio, 0.97; 95% confidence interval, 0.9-1.05, P = .48).

CONCLUSION AND CLINICAL

IMPORTANCE

Serum TK1 values were not predictive of lymphoma diagnosis in this cohort of horses.