Koomen BM, Voorham QJM, Epskamp-Kuijpers CCHJ, et al. - Researchers utilized real-world clinical pathology data on non-small cell lung cancer (NSCLC) patients to evaluate the extent of interlaboratory variation in programmed death-ligand 1 (PD-L1) positivity in the Netherlands, given immunohistochemical expression of PD-L1 serve as a predictive biomarker for prescription of immunotherapy in NSCLC. They analyzed histology data on 6,354 patients from 30 laboratories. The maximum interlaboratory variation, at the 1% cutoff, was reported to be 39.1% (32.7% - 71.8%) and ten laboratories (33.3%) varied significantly from the mean. The maximum variation, at 50% cutoff, was 23.1% (17.2% - 40.3%) and four laboratories (13.3%) differed significantly from the mean. Findings revealed considerable interlaboratory variation in PD-L1 positivity. Using the 1% cutoff was associated with the largest variation. At the 50% cutoff, cytology data evaluation revealed a higher degree of variation compared with the analysis of histology data.