Comparative assessment of manual chart review and ICD claims data in evaluating immunotherapy-related adverse events

Background The aim of this retrospective study was to demonstrate that irAEs, specifically gastrointestinal and pulmonary, examined through International Classification of Disease (ICD) data leads to underrepresentation of true irAEs and overrepresentation of false irAEs, thereby concluding that ICD claims data are a poor approach to electronic health record (EHR) data mining for irAEs in immunotherapy clinical research. Methods This retrospective analysis was conducted in 1,063 cancer patients who received ICIs between 2011 and 2017. We identified irAEs by manual review of medical records to determine the incidence of each of our endpoints, namely colitis, hepatitis, pneumonitis, other irAE, or no irAE. We then performed a secondary analysis utilizing ICD claims data alone using a broad range of symptom and disease-specific ICD codes representative of irAEs. Results 16% ( n = 174/1,063) of the total study population was initially found to have either pneumonitis 3% ( n = 37), colitis 7% ( n = 81) or hepatitis 5% ( n = 56) on manual review. Of these patients, 46% ( n = 80/174) did not have ICD code evidence in the EHR reflecting their irAE. Of the total patients not found to have any irAEs during manual review, 61% ( n = 459/748) of patients had ICD codes suggestive of possible irAE, yet were not identified as having an irAE during manual review. Discussion Examining gastrointestinal and pulmonary irAEs through the International Classification of Disease (ICD) data leads to underrepresentation of true irAEs and overrepresentation of false irAEs.