[Quick radioimmunoassay for plasma immunoreactive gastrin--application for localizing occult gastrinoma(s) during...

A rapid method for determining gastrin, quick gastrin, has been developed. Separation/washing procedure has been improved and can be completed within three minutes. It required only 48 minutes for the assay of 22 blood samples. Quick gastrin is a RIA that uses magnetic particles. On magnetic particles, a goat anti-rabbit IgG antibody is bound covalently. An anti-human gastrin rabbit antibody is bound to an anti-rabbit IgG antibody. Assay is started by adding the magnetic particles to a mixture of sample and 125I-gastrin. Following 30 minute incubation at 37 degrees C, the particles are sedimented in a magnetic field and washed. The gastrin content of the sample is then quantitated by counting radioactivity of the particles. Incomplete equilibration of antigen-antibody reaction is corrected using standard solution prepared from charcoal treated plasma. The immunoreactive gastrin values by quick gastrin correlated well with those by a commercial assay kit (Gammadab RIA kit; y = 1.01 x +4.3, r = 0.99). When compared to a reported conventional rapid assay, quick gastrin is easier and more accurate. Quick gastrin is sensitive enough to use for intra-operative determination of gastrin. We applied quick gastrin to the samples obtained from intra-operative secretin test in a gastrinoma patient. Twofold increases in gastrin after injection of secretin clearly indicated the existence of occult gastrinomas in her pancreas. When gastrin was assayed with the conventional rapid method, the increase in gastrin was less and did not reach the criteria for existence of gastrinoma.