Panel Reactive Antibody Screening Service

Evaluation of humoral sensitization, commonly determined by the panel reactive antibody (PRA) screening, is accepted as an important part of the pre-transplant assessment. Creative Biolabs provides PRA screening to identify human leukocyte antigen (HLA) antibodies in transplant candidates.

PRA Screening Assay

PRA assay, also known as HLA antibody screening or specificity identification testing, is performed for evaluation of the pre-sensitization status of transplant candidates.

Antibodies in sera can be identified by the PRA screen. In detail, microspheres are coated with two haplotypes of HLA class I or II antigens isolated from the surface of cell lines in their native (natural) conformation. The beads, loaded with varying amounts of florescent dye, are then incubated with serum. HLA displayed by the panel of microspheres is representative of the donor pool. HLA antibodies in the serum bind their specific antigen targets and are identified by multiplexed immunoassay technology. The result is the percentage of microspheres on the panel that is identified to react with HLA antibodies in the serum, termed percentage PRA as well as positive antibody specificities.

Characteristics of PRA Screening Assay

• PRA assay is a screening mechanism to determine the HLA antibody profile of potential transplant recipients.
• PRA assay is more sensitive than the cell-based cytotoxic antibody screen and less sensitive and specific than the HLA single antigen class I and class II bead test.
• PRA assay does not identify antibodies to low expression antigens such as HLA C, DP, or DR51/52/53.
• Sensitization of the recipient is expressed as the percentage of serum reactivity with the total panel. Typically, high PRA is indicative of a highly sensitized recipient- one who is at risk for early graft loss.

Application of PRA Screening Assay

• Pre-transplant

It is recommended to screen patients for PRA in specified intervals because anti-HLA antibodies vary with time in one individual patient and may be influenced by many factors. The intervals should not be more than 3 months. In case of blood transfusion, a sample should be tested between 14 to 28 days post-transfusion.

It can greatly help in predicting the cross­match results if PRA and antibody specificity are determined on a series of sera. Even patients who receive zero mismatches at HLA-A, B, and DR benefit from regular screening and antibody characterization. Antibodies specific to HLA­Cw, DQ, and even DP have been shown to influence graft outcomes.

• Post-transplant

Even though transplant patients receive immunosuppressive drugs, their immune system is still capable of mounting immune responses. De novo antibodies produced post-transplant are capable of rejection and chronic graft damage. Monitoring anti-HLA, antibodies post-transplant, especially donor-specific antibodies, can help in predicting graft outcomes.

As a leader in HLA antibody detection service, Creative Biolabs offers a full range portfolio of assays for low- to high-resolution detection. We also offer the most cost-effective multiplex assays and a wide range of singleplex kits. For more information, please feel free to contact us directly.