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We evaluated a commercial enzyme immunoassay kit for carcinoembryonic antigen (CEA) based on a non-competitive "sandwich principle" method (Abbott Laboratories). The serum sample is treated with an acid buffer and the supernate is incubated with an anti-CEA coated polystyrene bead. After washing, the bead is incubated with an anti-CEA/peroxidase conjugate. After a second washing, the activity of the enzyme bound to the solid phase is assayed after addition of a chromogenic substrate. This activity is proportional to the concentration of CEA in the serum sample. The characteristics of the assay are: (a) good sensitivity (around 0.25 microgram/L) and (b) satisfactory reproducibility (CV < 11% within assay). There is little cross reactivity between CEA and molecules such as nonspecific cross-reacting antigens that are known for their high potential of cross reactivity. No nonspecific interference was encountered with anti-globulin factors. We compared results with this enzyme immunoassay kit with those by a radioimmunoassay provided by the Commissariat à l'Energie Atomique. The correlation (r) was 0.95 (p < 0.001). The distribution of CEA values obtained for 1020 normal subjects is given. We conclude that the kit provides a simple and reliable procedure.

Determination of ornithine carbamoyl transferase (EC 2.1.3.3) activity in plasma is important for detection of liver diseases. The assay established in this paper has been made optimum. A blank is needed containing both substrates, carbamoyl phosphate and ornithine. We used a new colorimetric assay, based on a complex with a phosphoferric-antipyrine reagent and diacetyl monoxime, to measure the citrulline formed. The highly sensitive assay permits low activities to be determined accurately. Values for blood plasma from 425 supposedly healthy people, varied from 0 to 16 U/liter (95th percentile), and 27% of this population showed an activity of less than 2 µmol of citrulline formed per minute per liter, 2 U/liter being the limit of the method’s sensitivity.

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