Processing-Independent Analysis in the Diagnosis of Gastrinomas.

Background: This study evaluates whether a new analytic principle, processing-independent analysis (PIA), offers better specificity and sensitivity than the conventional gastrin radioimmunoassay in the diagnosis of gastrinomas. Methods: Plasma concentrations of α-amidated gastrins and the total progastrin product were measured with radioimmunoassay and with PIA, respectively, in 512 samples taken for gastrin measurement and in a selected group of gastrinoma patients (n = 10). Results: Among the 512 patients were 9 with gastrinomas. In plasma from these patients the median degree of amidation (ratio of α-amidated gastrins to total progastrin product) was 75% (range, 25-98%), whereas in the other groups the medians varied from 41% to 86%. In the second group of gastrinoma patients all had a degree of amidation of less than 50%. Conclusions: In screening for gastrinomas PIA offered no diagnostic advantages in comparison with conventional gastrin radioimmunoassay. However, in selected patients who in spite of normal or slightly increased concentrations of amidated gastrins were still suspected of having gastrinoma, additional measurement of the total progastrin product showed incomplete processing of progastrin and thus proved helpful in establishing the diagnosis. [ABSTRACT FROM AUTHOR]