[Extraordinary high elevation of serum CA19-9 levels in an apparently healthy subject]

We studied the woman presenting extraordinarily high serum CA19-9 levels who did not have any disease that was known to result in elevation of the serum CA19-9 level. Her CA19-9 values in sera obtained by 16 determinations with the enzyme immunoassay (EIA) over a period of 7 years were from 820 U/ml to 1,310 U/ml (median 1,015 U/ml). The correlation was good between serum CA19-9 levels in this subject with the EIA and radio immunoassay (RIA). The molecular weight of CA19-9 was determined by high-performance liquid chromatography (TSK gel G4000 SWXL column). While the molecular weights of CA19-9 in each patient with pancreatic cancer, cholangioma, cholecystitis or pancreatitis that were used as controls, were greater than 1,000 kDa, the CA19-9 of this subject had the molecular weight of approximately 550 kDa. To further determine whether human immunoglobulin was involved in the elevation of CA19-9 in the serum of this subject, we investigated the effect of adding rabbit anti-human IgM, IgG and IgA sera to the serum of this subject, CA19-9 values were unaffected by these antisera. Thus, the data obtained from the absorption study indicated that an anti-idiotypic antibody against the anti-CA19-9 antibody is unlikely to be responsible for an elevation of CA19-9 in the serum of this subject.