In safety studies, events reported as infections may be misclassified and, therefore, affect the validity of estimated risks associated with biologic agents. Using data from the Consortium of Rheumatology Researchers of North America (CORRONA), we evaluated hospitalized infection reports contributed by rheumatologists to establish their validity.
All patients hospitalized with infections from 2002 to 2007 reported to CORRONA were examined and compared with information from hospital discharge summaries and other confirmatory data. Infectious episodes were classified by two physicians as confirmed, empirically treated, possible or unlikely.
Of 562 reported hospitalized infectious episodes, 9% were classified as unlikely and had minimal or no supporting evidence for infection, leaving 509 hospitalized infectious episodes. Of these, 53% of the infectious episodes were classified as confirmed, 15% empirically treated and 32% possible. The confirmation status of infectious episodes for younger or biologic-exposed participants was similar to older and biologic-unexposed participants.
More than two-thirds of hospitalized infections reported by rheumatologists were confirmed or had evidence that the physician was treating an infection. In almost all cases, there was at least modest evidence for an infection. Future studies should consider case definitions for infections or sensitivity analyses, or both, regarding the certainty of an infection to account for possible misclassification and reduce bias.