title: Tumor marker radioimmunoassays in gastric juice. Methodologic drawbacks due to pH variations.
abstract: Conflicting data have been reported on tumor marker determination in gastric juice. In the present study the effect of pH variations on both antibody-antigen binding and the immunologic stability of the antigen were evaluated for the radioimmunoassay of carcinoembryonic antigen, CA19-9, tissue polypeptide antigen, and ferritin. A significant inhibition of antibody-antigen binding was constantly found in acidic conditions. Antigen concentration was lower in acidified than in untreated samples, possibly due to the carryover of acidity in the incubation mixture. Neutralization of acidified samples partly improved recovery of carcinoembryonic antigen and CA19-9. Tissue polypeptide antigen and ferritin were not recovered by neutralization in samples with pH less than 4.5, suggesting an irreversible damage of the immunologic characteristics of the two antigens. From the present data we conclude that an accurate validation of methods and a rigorous standardization of sample collection are mandatory for tumor marker determination by radioimmunoassay in gastric juice.
authors.affiliation: Division of Radiotherapy and Nuclear Medicine, Regional General Hospital, Venezia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Gion
authors.forename: R
authors.initials: R
authors.lastname: Dittadi
authors.forename: G
authors.initials: G
authors.lastname: Munegato
authors.forename: R
authors.initials: R
authors.lastname: Mione
authors.forename: G
authors.initials: G
authors.lastname: Gurnari
authors.forename: E F
authors.initials: EF
authors.lastname: Zotti
authors.forename: G
authors.initials: G
authors.lastname: Bruscagnin
mesh_terms: D000911:Antibodies, Monoclonal; D000937:Antigen-Antibody Reactions; D000951:Antigens, Neoplasm / Q000032:analysis / Q000378:metabolism; D000954:Antigens, Surface / Q000032:analysis / Q000378:metabolism; D015295:Antigens, Tumor-Associated, Carbohydrate; D002272:Carcinoembryonic Antigen / Q000032:analysis / Q000378:metabolism; D005293:Ferritins / Q000032:analysis / Q000378:metabolism; D005750:Gastric Juice / Q000032:analysis* / Q000378:metabolism; D005770:Gastrointestinal Neoplasms / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010455:Peptides / Q000032:analysis / Q000378:metabolism; D011863:Radioimmunoassay; D019396:Tissue Polypeptide Antigen
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D015295:Antigens, Tumor-Associated, Carbohydrate; D002272:Carcinoembryonic Antigen; D010455:Peptides; D019396:Tissue Polypeptide Antigen; D005293:Ferritins