No abstract

Background We described a patient who exhibited a gradual increase in carbohydrate antigen 19‐9 (CA19‐9) concentrations for 4 years at three hospitals, with no associated clinical manifestations; however, we were unable to define the cause of this increase, forcing us to consider whether it was a false‐positive result. Methods Given the potential for interference, this study used multiple system detection, gradient dilution, Polyethylene glycol (PEG) precipitation and heterophilic antibody blocking assay to evaluate the reliability of CA19‐9 concentration increase. Results Analysis of the patient sample using multiple systems indicated that CA19‐9 concentrations showed an obvious increase (154.0, and 889.2 IU/ml, respectively) using the Cobas E602 and Advia Centaur XP systems, and were within the reference ranges (<10 IU/ml) on other modules. PEG precipitation on the Cobas E602 and Advia Centaur XP systems reduced the CA19‐9 concentration, as did heterophilic blocking tube (HBT‐6, HBT‐1) blockade. Conclusion CA19‐9 was incorrectly identified to increase due to the presence of heterophilic antibodies. We recommend that heterophilic antibodies should be evaluated in cases with elevated CA19‐9 level but no associated clinical manifestations to prevent false positives.