Estimating the incidence and duration of diagnostic delays for measles

OBJECTIVE: Although measles was declared eliminated in the United States in 2000, cases have increased in recent years. Our goal was to estimate the incidence and duration of diagnostic delays for measles and identify factors associated with delays. DESIGN: Case-crossover. SETTING: We used the Merative MarketScan Research Databases (2001-2023). PATIENTS: We identified measles cases and evaluated prior healthcare encounters for potential missed diagnostic opportunities. METHODS: Using a bootstrapping approach, we estimated the number of healthcare visits representing possible missed opportunities to diagnose measles during a two-week period preceding the index diagnosis. We utilized Firth logistic regression to assess factors associated with delays. RESULTS: We identified 4,651 measles cases. During the two-week period prior to diagnosis, 426 (9.2%) patients had healthcare visits with signs or symptoms commonly associated with measles. We estimated 381 (95%CI: 330-440) missed opportunities to diagnose measles. Delays occurred most frequently in outpatient settings (81.0%). Approximately 6.9% (95%CI: 6.1-8.0%) of patients experienced at least one missed opportunity, with a mean delay of 4.05 days (95%CI: 3.48-4.51) (median delay = 2.94 days [95%CI: 2.00-3.00]). An estimated 1.7% (95%CI: 1.1-2.2%) of patients experienced a diagnostic delay lasting a week or longer. Factors associated with an increased likelihood of delays included age <2 years and receiving antibiotic prescriptions. CONCLUSIONS: Diagnostic delays for measles are not uncommon and may facilitate transmission, especially in outpatient settings.