Lipemia and serum index-related interference in Luminex-based anti-HLA antibody detection.

BACKGROUND: Luminex bead-based solid-phase immunoassays (SFIA) are the gold standard for anti-human leukocyte antigen (HLA) antibody detection in transplantation immunology. However, preanalytical interferences may compromise assay validity. Although automated hemolysis, icterus, and lipemia (HIL) indices are routinely used to assess sample quality, their relevance for predicting interference in Luminex-based HLA antibody testing remains unclear. METHODS: A total of 1308 patient samples were retrospectively evaluated using Luminex SFIA. Internal control bead mean fluorescence intensity (MFI) values were assessed according to manufacturer-defined criteria. Samples with control bead deviations were analyzed in relation to automated HIL indices and categorized into four interference profiles based on control bead behavior. Control bead normalization ratios and correlation analyses were performed. RESULTS: Control bead MFI values outside acceptable ranges were observed in 125 samples (9.7%). After exclusion of 16 samples, 109 were included in the final analysis. Elevated lipemia indices were associated with assay interference in two groups, manifesting as signal amplification or signal quenching. Notably, more than half of the deviated samples showed marked signal suppression despite normal HIL indices, consistent with silent interference. Another interference profile demonstrated pronounced control bead signal elevation in the absence of abnormal HIL indices, indicating an index-independent matrix effect. CONCLUSION: Lipemia represents an underrecognized source of interference in Luminex-based HLA antibody testing. Automated HIL indices alone did not capture all analytically compromised samples in this cohort. Systematic monitoring of internal control bead values may improve detection of silent and index-independent interferences and enhance analytical accuracy.