Abstract
Context An immunohistochemistry (IHC) assay developed to detect lymphocyte-activation gene 3 (LAG-3), a novel immune checkpoint inhibitor target, has demonstrated high analytical precision and interlaboratory reproducibility using a Leica staining platform, but has not been investigated on other IHC staining platforms.
Objective To evaluate the performance of LAG-3 IHC assays using the 17B4 antibody clone across widely used IHC staining platforms: Agilent/Dako Autostainer Link 48 (ASL-48) and VENTANA BenchMark ULTRA (VBU) compared with Leica BOND-RX (BOND-RX).
Design Eighty formalin-fixed paraffin-embedded melanoma tissue blocks were cut into consecutive sections and evaluated using staining platform–specific IHC assays with the 17B4 antibody clone. Duplicate testing was performed on the BOND-RX platform to assess intraplatform agreement. LAG-3 expression using a numerical score was evaluated by a pathologist and with a digital scoring algorithm. LAG-3 positivity was determined from manual scores using a ≥ 1% cutoff.
Results LAG-3 IHC staining patterns and intensities were visually similar across all 3 staining platforms. Pearson correlation was ≥ 0.88 for interplatform and BOND-RX intraplatform concordance when LAG-3 expression was evaluated with a numerical score determined by a pathologist. Correlation increased with a numerical score determined with a digital scoring algorithm (Pearson correlation ≥ 0.93 for all comparisons). Overall percentage agreement was ≥ 77.5% for interplatform and BOND-RX intraplatform comparisons when a ≥ 1% cutoff was used to determine LAG-3 positivity.
Conclusions Data from this study demonstrate that LAG-3 expression can be robustly and reproducibly assessed across 3 major commercial IHC staining platforms using the 17B4 antibody clone.
Competing Interest Statement
This study was supported by Bristol Myers Squibb. JW, KD, LD, and JB are employees of and own stock in Bristol Myers Squibb. KA, GG, AV, and CR are employees of CellCarta.