An adaptive quantification scheme for profiling serum antibody level in transplant immunology

Area of Science:

• Transplantation immunology
• Immunogenetics
• Clinical diagnostics

Background:

• Luminex single antigen bead (SAB) assays are crucial for detecting HLA-specific antibodies in transplantation.
• The relative nature of SAB assay signals (MFI) complicates interpretation and comparability.
• Fixed cutoffs for SAB results are problematic due to inherent variability and signal drift.

Purpose of the Study:

• To introduce Density-driven Adaptive Quantitative Score (DAQS), a novel framework for antibody quantification.
• To address the limitations of Mean Fluorescence Intensity (MFI) in SAB assay interpretation.
• To improve the comparability and reliability of HLA-specific antibody assessments.

Main Methods:

• Development and application of the DAQS framework, a distribution-based scoring system.
• Analysis of 388 HLA-class I and 394 HLA-class II SAB measurements.
• Validation using longitudinal patient data, technical replicates, and external proficiency testing (EPT) data from two laboratories.

Main Results:

• DAQS stabilizes scores, particularly for strongly reactive beads, reducing variability compared to MFI.
• DAQS detected anti-donor HLA-specific antibodies (DSA) even when MFI values declined significantly.
• DAQS demonstrated correction for technical bias while preserving biological variability.

Conclusions:

• DAQS offers adaptive, context-aware scoring for antibody presence, enhancing interpretation.
• DAQS improves the comparability of SAB assay results across different time points and laboratories.
• DAQS provides a more reliable method for assessing immunological status in transplantation medicine.