A case study of suspected heterophilic interference in serum CA19-9 in immunoassay: Recommended method

Background

We reported a patient who exhibited an abnormal increase in carbohydrate antigen 19–9 (CA19–9) concentrations for 5 years in our hospital without matched clinical symptoms. We considered whether it was a false-positive result.

Methods

To identify the potential interference, multiple platform detections, gradient dilution, polyethylene glycol (PEG) precipitation and heterophilic antibody blocking assays were respectively used to evaluate the true CA19–9 concentration.

Results

The CA19–9 concentration showed an obvious increase (189.9 U/mL) using the Architect i2000SR platform while it was within the reference ranges on the Cobas e801 and DXI800 platforms. PEG precipitation effectively corrected the false CA19–9 concentration, as did the heterophilic blocking tube (HBT).

Conclusion

The CA19–9 concentration of this patient was identified to be interfered with by the presence of heterophilic antibodies. The lesson learned from this case is that false positives should be vigilant when using immunoassays to detect markers, especially in patients without corresponding clinical symptoms. Three types of experiments against heterophilic interference, gradient dilution, PEG precipitation, and blockers, are highly operational and effective in clinical laboratories.