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Immunoradiometric assay (IRMA) using monoclonal antibody for colon cancer cell surface antigen (CA19-9) was compared with carcinoembryonic antigen (CEA) with regard to sensitivity and specificity in 730 patients. In the 341 patients who had no evidence of malignant disease, CA19-9 levels ranged between 4. 5 to 49 U/ml. Specificity of CA19-9 at a cutoff of 20 U/ml was similar to that of CEA at a cutoff of 5.0 ng/ml; CA19-9 was more sensitive than CEA in pancreatic cancer, whereas CEA was more sensitive than CA19-9 in breast, colon, and gastric cancer. Of 17 patients with pancreatic cancer, 13 had elevated levels of CA19-9 (sensitivity, 76%). whereas only 8 had elevated levels of CEA (sensitivity, 47%) and 15 had elevated levels of either CEA or CA19-9 (sensitivity, 88%). These findings suggest that, like CEA, CA19-9 is detectable in nonmalignant diseases and is not specific for gastrointestinal tumors, and has higher sensitivity than CEA only in pancreatic cancer. However, further prospective studies are required to verify its value in the diagnosis and management of pancreatic cancer. Cancer 56977-283, 1985. LTHOUGH carcinoembryonic antigen (CEA) has A been the most widely studied'-3 and used marker in human cancer, it lacks the specificity and sensitivity required for early detection of malignan~y.~ Clinically, it is used only as an indicator of recurrence or as a monitor of therapy in known cancer More recently, hybridoma technology* has renewed interest in more specific tumor markers. Koprowski et al. developed a monoclonal antibody to colon cancer cell surface antigen in 19799 and later showed that this antibody reacted with sialylated lacto-N-fuco-pentoase 11. l o In early clinical studies, this same antibody has been found to be both highly sensitive and specific in identifying gastrointestinal adenocarcinoma.'1*'2 A radiometric assay using this antibody has been made available for inves-tigational purposes (along with the necessary reagents) by Centocor (Philadelphia).'' In this report we present our results with this assay, including comparison with CEA, in patients with malignant and nonmalignant diseases. Materials and Methods Immimoradiometric Assay for CA19-9 Details of the CA19-9 assay have been described previously. Briefly, antibody coated beads were incu-bated with standards and unknowns (100 pl) in 25 well reaction trays for 3 hours at 37°C. The beads were then washed and 200 ~l of radiolabeled iodine 125 ('251) anti-CA19-9 (approximately 100,OOO cpm) was added to each bead. The beads were incubated for 3 hours at room temperature, followed by aspiration and washing, after which they were transferred into 12 X 75 mm tubes and counted in a gamma counter. The lowest 277

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In recent years, especially since the advent of the electron microscope, there has been a renewed interest in the morphologic and functional aspects of a variety of experimental and human renal diseases associated with proteinuria. An excellent experimental model for such studies has been the renin-induced proteinuria in the rabbit and the rat. In 1940, Pickering and Prinzmetal (1) reported that parenteral administration of renin, the renal enzyme implicated in experimental renal hypertension, induced a marked diuresis in the rabbit, accompanied by increased rate of sodium and chloride excretion and a significant degree of proteinuria. Brandt and Gruhn (2) confirmed this observation, and by studying the simultaneous excretion of injected hemoglobin, concluded that the proteinuria was caused by diminished tubular reabsorption of protein from the glomerular filtrate and not by altered glomerular permeability. Shortly afterwards, Addis et al. (3) discovered that renin produced an intense proteinuria in the rat also and, from a combination of morphological and functional data obtained by these workers and by others, it was concluded that renin produced this effect mainly by increasing glomerular permeability. Thus, conflicting views have been expressed concerning the mechanism by which renin produces an increased excretion of protein in the urine.Previous studies on the relationship between the pressor and proteinuric activities of renin have also led to similar conflicting results. Thus, Addis et al. (3) suggested that the proteinuria was dependent on the pressor activity of renin, since inhibition of this activity by heat also abolished the proteinuric effect. On the other hand, Sellers et al. (4) concluded that "the proteinuric property of renin is not related to the ability of this compound to elevate