AroCell TK 210 ELISA for determination of TK1 protein: age-related reference ranges and comparison with other TK1 assays

Thymidine kinase 1 (TK1) is an enzyme involved in DNA precursor synthesis that has been used as a biomarker for prognosis and monitoring of different malignancies. In this study, we compared two immunoassays for measuring TK1 protein concentrations: the TK 210 ELISA (AroCell AB) and TK1 ELISA from Abcam. Overall, the TK 210 ELISA showed higher sensitivity than the Abcam TK1 ELISA for differentiating hematological malignancies (sensitivity of 0.77 vs 0.45) as well as for distinguishing sera of patients with solid tumors from those of apparently healthy individuals (0.61 vs 0.20). There was no significant difference in the TK1 protein levels determined with the TK 210 ELISA between different age groups from apparently healthy individuals. These results strongly indicate that the AroCell TK 210 ELISA is accurate and sensitive enough to be a valuable tool in cancer management.METHOD SUMMARYThymidine kinase 1 (TK1) is an enzyme that leaks from S phase cells as a result of high cell turnover. Commercially available TK activity assays have certain limitations; to overcome these, we developed a dual monoclonal antibody-based ELISA, the AroCell TK 210 ELISA, which is commercially available. The ELISA includes a preincubation procedure with a special buffer that reduces high molecular weight complexes of serum TK1 and exposes the TK1 epitope to facilitate antibody binding. This provides a robust and convenient assay for the determination of TK1 protein concentrations in sera from patients with different malignancies.