[CA-50 in serum of patients with carcinoma. Clinical experiences with a new tumor marker].

Quantitative radioimmunological demonstration of carbohydrate antigen CA-50 in serum achieved a sensitivity of 62.3% for colorectal carcinoma (n = 53), of 64.7% for gastric carcinoma (n = 34), of 33.9% for lung carcinoma (n = 56), and 19.8% for lymphoproliferative diseases (n = 91). The positive results for the latter probably correspond to the immunohistological demonstration of the antigen in dendritic reticulum cells. Occasionally an increased CA-50 level in inflammatory disease presents difficulties in differential diagnosis, but it returns to normal when the inflammatory process has subsided. Methodological scatter of the CA-50 system is satisfactory, with a coefficient of variation of +/- 11%, but unsatisfactory at low values (less than or equal to 10 U/ml) and high ones (greater than or equal to 50 U/ml) with a coefficient of variation of +/- 19%. Further development with the IMRA technique may significantly reduce methodological scatter (coefficient of variation +/- 5%).