Improved Detection of HLA-DP Antibodies: Comparative Evaluation of LIFECODES LifeScreen Deluxe and LifeScreen XP in Class II Anti-HLA Antibody Screening

Dear Editor,

Human leukocyte antigen (HLA) donor specific antibodies (DSA) detection is crucial in minimizing immunological risk and improving graft outcomes in renal transplantation.^1,2 Anti-HLA antibody screening is a critical step prior to confirmatory testing at many transplant immunology laboratories.³ We report a comparative evaluation of two anti-HLA antibody screening kits: LIFECODES LifeScreen Deluxe (LMX) and newer LifeScreen XP (LMXP), in renal transplant recipients.

A total of 70 de-identified archived known anti-HLA antibody-positive (n=52) and negative (n=18) remnant samples from kidney transplant recipients were analyzed using both LMX and LMXP kits. Of these 52 samples, anti-HLA-DP antibodies were identified in four cases. Results of all 70 samples were compared in both LMX and LMXP, against the Luminex Single Antigen Bead (LSA) assay, which was considered the “gold standard” for the current analysis. The comparison of anti-HLA antibody screening results obtained using LMX and LMXP kits with the LSA assay (considered the gold standard) has been illustrated in Table 1.

LMXP showed improved sensitivity (60%) over LMX (52%), particularly in detecting HLA-DP antibodies. LMXP detected three additional positive samples, including two HLA-DP antibody-positive cases that LMX missed, highlighting its enhanced screening capability. This improvement was due to the inclusion of two additional beads (CII06 and CII07) in LMXP, designed specifically for HLA-DP antibody detection. Specificity was slightly higher in LMX (75.56%) compared to LMXP (73.33%). LMXP exhibited superior overall diagnostic performance, with a higher positive likelihood ratio (2.25 vs. 2.13) and better agreement with the gold standard assay (κ = 0.328 vs. 0.278). Both kits use undiluted serum (12.5 μL sample, 5 μL reagent) with comparable incubation times, wash steps, and hands-on time. The primary distinction lies in the expanded bead panel in LMXP, improving HLA-DP antibody detection. A positive result for the LMX and LMXP tests may be caused by antibodies against any one of the three HLA class II antigens (DP, DQ, and DR) or by a combination of these. However, because the SAB assay identifies DR, DQ, and DP antibodies independently, a sample that tests positive for HLA-DQ will not test positive for HLA-DR or DP antibodies. These results support the use of newer LMXP over LMX by virtue of being a more sensitive screening tool in pre-transplant compatibility testing. Confirmatory testing with LSA may be required in patients tested positive by LMXP, before releasing the final pre-transplant compatibility test report.