Evaluation and Revision of Historical ESSENCE Syndromic Surveillance Definition Used to Identify Work-Related...

Occupational health surveillance programs have rarely incorporated syndromic surveillance. We documented a process for evaluating and revising syndromic surveillance definitions, using the example of work-related emergency department (ED) visits.

Of 140 331 481 ED visits in the National Syndromic Surveillance Program from May 15, 2016, through October 31, 2017, we extracted 391 827 records for phase 1 that met the previously unevaluated original work-related definition or included a work-related employment status ICD-10-CM code (Y99.0/Y99.1; International Classification of Diseases, Tenth Revision, Clinical Modification). Also for phase 1, we evaluated the performance of the original work-related definition using ICD-10-CM work-related employment status codes as a reference standard. In phase 2, we extracted 99 109 records containing candidate work-related keywords. Finally, in phase 3, we examined individual keywords and developed and evaluated a revised definition.

The revised work-related definition identified 259 153 visits by keyword alone, 104 342 visits by ICD-10-CM work-related employment status codes alone, and 16 385 ED visits by both methods. Sensitivity (13.6% vs 11.3%) and positive predictive value (5.9% vs 4.8%) were higher for the revised definition than for the original work-related definition. Manual review indicated that 91.3% (95% CI, 89.6%-93.0%) of visits identified by the revised definition keywords met the study criteria for work-related visits as compared with 75.5% (95% CI, 73.0%-78.4%) of visits for the original work-related definition.

The original work-related definition performed suboptimally because keywords were not sufficiently specific. The revised definition is an improvement but requires testing in real-world scenarios. The presented methods for developing a syndromic surveillance definition are useful, not only for occupational health, but for identification of other subpopulations treated in the ED.