[False elevations of C-reactive protein: When should they be considered?]

C-reactive protein (CRP) is the key biomarker for diagnosing and monitoring inflammatory conditions. However, challenges arise when patients exhibit elevated CRP levels without an evident inflammatory cause. Despite the performance of CRP assays using immunoturbidimetry, this method remains sensitive to interferences that may result in false positive results.

Drawing from three case studies illustrating analytical interferences in CRP measurements, we propose a comprehensive review of the literature on this subject. The most common cause of analytical interference in CRP measurement is the binding of rheumatoid factor to capture antibodies, generating a signal detected by immunoturbidimetry despite the absence of CRP in the sample. To identify such interferences, various antibody neutralization techniques and alternative assay methods can be employed. Reporting falsely elevated CRP levels may lead to unnecessary and potentially invasive diagnostic procedures, causing undue patient anxiety. Moreover, erroneous laboratory results can result in diagnostic errors or the initiation of inappropriate therapies, contributing to patient harm and additional healthcare costs.

Unexplained and persistent elevation of CRP levels, particularly in the absence of other inflammatory markers and clinical evidence, should raise suspicion of analytical interference and prompt immediate discussion between clinicians and medical biologists to clarify the situation.