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Background: When CA199 is solely elevated, it may be a false increase due to interference. Rheumatoid factor (RF), an autoantibody binding to the Fc fragment of denatured IgG, can interfere with immunological tests.
Methods: Chemiluminescent immunoassay was used to detect tumor markers. For this patient, to exclude false CA199 elevation, PEG precipitation, serial dilution, and platform switching were applied.
Results: In the PEG precipitation test, the patient's sample formed flocs. Post-PEG treatment, CA199 dropped from 179.62 U/mL to 17.66 U/mL (9.83% recovery), suggesting interference. Serial dilution showed a non-linear CA199 relationship, further indicating interference. Platform switching revealed significant results: Abbott's platform measured CA199 at 179.62 U/mL, while Mindray's was 18.68 U/mL.
Conclusions: RFis an IgG antibody and can disrupt immunological tests. When encountering high RF in reports, consider its interference on other immunological tests. Use methods like sample dilution, spiking/recovery tests, platform switching, and comparing related test results to verify interference and ensure detection accuracy.
DOI: 10.7754/Clin.Lab.2025.250356
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