HLA Antibody Testing

Antibody Identification

To detect specificity and strength of HLA antibodies in recipient candidates to determine calculated panel reactive antibodies (cPRA) value.
To identify compatible organ donors.
To identify compatible donors for transfusions.
To detect and monitor donor-specific HLA antibodies (DSA) after transplantation.

Antibodies directed against over 120 distinct core HLA allotypes are measured using Luminex-based single antigen bead (SAB) assay.
The ITL has extensive expertise in HLA antibody identification. The laboratory has performed SAB class I and class II assays on over 35,000 samples in the past 5 years, with a current monthly average volume of > 800 samples.
A high throughput liquid handling system is used to minimize inter-assay variations in median fluorescence intensity (MFI) values.
Antibody specificity is determined based on sequence homologies and cross reactivity patterns.
SAB assay that yields unusual results is retested with SAB and/or a multi-antigen bead assay from other vendors to confirm antibody specificities.
The reported MFI which is used as an arbitrary unit of antibody quantity is the adjusted MFI. The average MFI of all positive beads is used to quantify the antibody if multiple beads have allelic variants of the same antigen (e.g., HLA-A*02:01, *02:03, and *02:06 - variants of HLA-A2 antigen).
The antibody test report:

1. Lists detected HLA antibody specificities including Bw4/Bw6 broad specificities, DQ-alpha, DP-alpha and allele-specific antibodies, and their corresponding MFI values.
2. Groups antibody specificities in three strength categories based on expected correlation with crossmatch outcomes: strong antibodies (MFI >8,500; may cause positive CDC and positive flow crossmatch), moderate level antibodies (MFI 2,000-8,499; may cause negative CDC crossmatch but positive flow crossmatch), and weak antibodies (MFI 1,000-1,999; do not cause a positive crossmatch).
3. Lists HLA types of the patient and previous organ donors (if available).
4. Lists the serum-specific cPRA value.

The post-transplant antibody test report identifies DSA and their MFI strength and a table and a graph showing all mismatched antigens, and the trend of donor-specific HLA antibodies (in MFI) in samples collected over various pre- and post-transplant time points.

(assuming samples received before 10:00 am)

ITL performs PRA screening tests with multi-antigen beads using reagents different from what is used in single antigen antibody identification to check for consistency.
The multi-antigen bead assay reports percent PRA in serum sample.
ITL uses liquid handling system to reduce technical variations and increase efficiency.

(assuming samples received before 10:00 am)