Enzyme-linked immunosorbent assay and radioimmunoassay of serum pepsinogen A

Abstract

The determination of serum pepsinogen A (=pepsinogen I) levels is of clinical importance in the study of duodenal ulcer, atrophic gastritis and gastric cancer. In the present study two different quantitative immunological techniques for serum pepsinogen A were compared: a radioimmunoassay (RIA) (Helsinki) and an enzyme-linked immunosorbent assay (ELISA) (Amsterdam). Serum samples of 177 subjects with various gastric diseases were tested in a double blind study. The correlation was excellent (r=0.954 in the range 0–760 μ;g/l and r=0·971 in the range 0–100 μg/l). The functional relationship between ELISA (x) and RIA (y), determined by weighted model II regression, was y=1.12x—0·54. Initially the use of goat anti-PGA in the ELISA resulted in falsely high values in about 10% of the individuals. This was caused by circulating antibodies cross-reacting with goat IgG. This artefact was eliminated by pre-incubation of all samples with non-immune goat serum.

Key words:

• ELISA
• immunoassay
• pepsinogen A
• pepsinogen I
• RIA