[Evaluation of time-resolved fluorometric immunoassay of CA 50]

Serum CA 50 was determined by a time resolved fluorometric immunoassay (TR-FIA) with CANAG CA-50 DELFIA kit. Evaluation of the assay system gave satisfactory results in its sensitivity, accuracy, reproducibility, dynamic range and easy handling. No prozone phenomenon was observed up to 347,000 U/ml. From a histogram of 134 normal sera, the cut off point was determined at 34 U/ml. CA 50 in 202 patients' sera was determined with this assay. Nineteen of 20 patients pancreatic cancer, 6 of 21 gastric cancer, 14 of 25 hepatoma gave positive values. In comparison with CA 19-9, higher values and higher rates of positive CA 50 were observed in benign and malignant liver diseases, suggesting its non-cancerous origin in the liver. A high correlation was observed between the level of CA 50 and CA 19-9 of 157 patients' sera. Serum CA 50 was completely correlated with CA 19-9 in the clinical course of patients with pancreatic cancer, but not in patients with hepatoma. Thus we conclude that the CANAG CA-50 DELFIA System is useful for the diagnosis and monitoring cancer patients but must be used with care because of its elevation in benign liver diseases.