[Analysis of the Squamous Cell Carcinoma Antigen (SCCA) Which Has a Significant Difference in Values between CLIA and FEIA--Case Report of Extra Glycosylation in SCCA].

Squamous cell carcinoma antigen (SCCA) is a glycoprotein that belongs to the serine protease inhibitor family. Clinically, it has been utilized as a tumor marker for squamous cell carcinoma. In clinical laboratories, SCCA is measured by several immunoassays. Recently, a number of studies have been reported that there is a significant difference in values between the immunoassays, attributing to SCCA-immunoglobulin complex. We found a case with significant difference in the SCCA value between CLIA and FEIA. In this case, SCCA-Immunoglobulin complex was not confirmed by gel filtration analysis. Interestingly, 5 to 10 kDa slightly-high molecular weight SCCA compared to control was detected by immunoblotting assay. It may be suspected that the aberrant glycosyl modification of SCCA influenced the reactivity to immunoassays.