text: [Studies of clinical usefulness of new tumor markers of ovarian cancer, CA 54/61 and CA 602--CA 602 assay reagent kit, performance its normal value and correlations with other tumor markers].
  We made a preclinical study of a newly developed tumor maker, CA 602, and its clinical study using serum samples available from 58 institutions located throughout Japan. In the preclinical study, a CA 602 assay kit was investigated for the reproducibility and precision of assay results; and in the clinical study, the kit was investigated for the normal value of the marker, for variations in assay result with age, menstrual cycle and term of pregnancy, and for correlations of assay results with those of other tumor markers. The tests of the kit for simultaneous reproducibility and interval reproducibility of assay results, and the results of analytical recovery and dilution tests were all favorable; the kit proved to be reliable in both precision and reproducibility. For the study, 2 cutoff levels were set: mean + 2 SD of healthy subjects, i.e., 63 U/ml, and the level which permits the maximal efficiency of differential diagnosis of benign from malignant ovarian tumors, i.e., 90 U/ml. The assay results showed that CA 602 levels were low in women aged 50 and over; the levels were high in the first half of pregnancy, and also high in the menstrual period to the early follicular phase. The assay results of CA 602 also proved to be intimately correlated with those of CA 125, which suggested that the 2 markers might be analogous to each other. CA 602 proving to be of high reproducibility even in the range of concentrations below the cutoff value, the measurement with the marker appeared to be of high precision, capable of detecting even the slightest variations in the antigen. CA 602 therefore appears of great value in the early detection of recurrent ovarian cancers.