Validation of Immune‐Related Adverse Event (<scp>irAE</scp>) Case Definitions in a Real‐World Lung Cancer Population

In this validation study of five irAE case definition algorithms, a combination of ICD-10 codes and medication administration codes generally perform well to identify more severe irAE (CTCAE Grade 3-5), and severe pneumonitis, hepatitis, and colitis (common irAEs) among all possible irAE severity levels and sites. Medication codes alone perform well at identifying severe irAE, while the most stringent algorithm (mirroring guideline-recommended irAE treatment) has the highest Sp and PPV. Algorithms have utility for comparing the relative risk of irAE between regimens or patient subgroups.