[A case of hepatoma patient who showed an abnormally high level of serum IRI with the beads method].

Abstract

A fifty four years old hepatoma patient admitted to the hospital for a surgical operation. Preoperative laboratory examination demonstrated that his serum IRI level was very high (423 microU/ml) when measured with a beads method, however RIA or a microplate method demonstrated normal values. We studied the mechanism of the discrepancy of IRI values. 1) Both the beads and microplate methods demonstrated the same IRI values when the patient's serum insulin was roughly purified with Sep-Pak. The beads method showed high IRI values in serum which passed through Sep-Pak, therefore contained no insulin. 2) The similar results were observed when the patient's serum fractionated by a gel-chromatography (Biogel P-30). The beads method demonstrated high IRI values in both insulin fractions and the fractions containing serum proteins bigger than 40,000 molecular weight. The microplate method demonstrated only one large peak of insulin. 3) When non-specific IgG of guinea pig was used as a fixed antibody instead of human insulin antibody of guinea pig that was used in the beads method, the patient's serum showed the similar values as that obtained with the beads method. We thereby concluded that the abnormal level of IRI by the beads method was derived from the unknown substance reacting with IgG of guinea pig in the patient's serum. After the surgical resection of hepatoma, the levels of IRI measured by the beads method decreased significantly, suggesting that the substance is related to hepatoma cells.