Predicting flow cytometry crossmatch results from single-antigen bead testing.

Area of Science:

• Immunology
• Transplantation Science
• Clinical Chemistry

Background:

• Flow cytometry crossmatch (FCXM) is crucial for assessing transplant compatibility.
• Predicting FCXM results using pre-transplant antibody screening can optimize resource allocation.
• Single-antigen bead (SAB) assays provide detailed human leucocyte antigen (HLA) antibody information.

Purpose of the Study:

• To develop and validate an algorithm for predicting FCXM results based on SAB mean fluorescent intensity (MFI).
• To correlate SAB MFI levels with established National External Quality Assurance Scheme (NEQAS) crossmatch outcomes.
• To establish predictive models for both T cell and B cell crossmatches.

Main Methods:

• Retrospective analysis of 159 serum samples and 40 HLA-typed peripheral blood samples from NEQAS proficiency testing (2019-2023).
• Screening using LABScreen Single Antigen (SAB) and HLA typing with LABType SSO.
• Development of predictive algorithms by combining HLA Class I and/or Class II MFI values, validated using receiver operating characteristic analysis.

Main Results:

• A combined HLA Class I MFI >5000 accurately predicted T cell crossmatch (96% sensitivity, 100% specificity).
• For B cell crossmatch prediction, HLA Class I + Class II MFI >11,000 showed high accuracy (97% sensitivity, 82% specificity).
• Optimized models for B cell prediction, particularly for HLA Class II sensitization, demonstrated high sensitivity and specificity.

Conclusions:

• SAB MFI levels can reliably predict FCXM outcomes, particularly T cell crossmatches.
• The developed algorithm offers a valuable tool for estimating immunological risk from donor-specific antibodies when FCXM is not feasible.
• This predictive model enhances pre-transplant risk assessment and resource management in transplantation.