Validation and comparison of tumor-associated trypsin inhibitor (TATI) immunoassays

Background: Tumor-associated trypsin inhibitor (TATI) is mainly proposed as a tumor marker for ovarian cancer. However, recent discoveries of TATI in cancer and inflammatory diseases show that assay of TATI in biological samples is of increasing interest. Methods: We validated a previously described TR-IFMA and a newly developed dual-monoclonal sandwich ELISA for TATI. These methods were compared with a commercial radioimmunoassay (RIA). We studied pre-analytical factors affecting serum TATI concentrations and established age- and gender specific reference intervals using serum samples from 195 healthy volunteers. Results: The assay range and precision were 0.8-45 mu g/L and < 9.1% for the ELISA, and 0.13 mu g/L-150 mu g/L and < 12.5% for the TR-IFMA, respectively. Both assays correlated well with a RIA. Type of blood sample and nutritional status were not critical and TATI was stable in serum samples when stored at + 4 degrees C and - 20 degrees C for 4 weeks and at - 80 degrees C for 8 weeks. The 95% reference limits for serum TATI in adults were 5.2-15.3 mu g/L in the age group 18-70 years and 7.5-21.3 mu g/L in the age group > 70 years. Conclusions: Significantly higher concentrations of serum TATI were observed in elderly women and in men. Both ELISA and TR-IFMA technologies can be employed to develop sensitive and robust immunoassays for TATI using monoclonal antibodies. (C) 2012 Elsevier B.V. All rights reserved.