Case report reveals rheumatoid factor can falsely elevate CA199 levels, suggesting significant interference in immunological tests.
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. 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. 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. 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.
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Sun et al. (2025) studied this question.
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