OBJECTIVES: To validate the representativeness of a social-media population for outcomes research, we performed a deterministic linkage study between an online survey population of multiple sclerosis (MS) patients and large claims data sources in the United States (US). METHODS: US patients with MS were recruited into a patient-reported survey by advertisements placed on Facebook. Eligibility criteria were a specialist diagnosis of MS (primary progressive, relapsing-remitting or secondary progressive); ≥12 months history of disease; age 18-65 years and commercially insured. All data were de-identified upon entry into the database. Data were gathered on demographic and disease characteristics, current and earlier therapies, relapses, disability, health related quality of life and employment status and productivity. A unique anonymous profile was generated for each survey respondent using a complex de-identification approach with multiple layers of encryption. Each anonymous profile was linked to a number of medical and pharmacy claims datasets in the US. Linkage rates were assessed and survey responders’ representativeness was evaluated based on the distribution of characteristics between the linked survey population and general MS populations in the claims databases. RESULTS: The advertisement was placed on 1,063,973 Facebook users’ pages generating 68,674 clicks, 3,719 survey attempts and 651 successfully completed surveys, of which 440 could be linked to any of the claims databases for 2014/15 (68% linkage rate). The linked population was slightly older and more likely to be female than the overall claims database MS population. There was a high degree of similarity on distributions of symptoms, comorbidities, medication use, relapse rates and costs. CONCLUSIONS: Linking a social-media driven survey population to claims databases enabled rapid gathering of a large population of representative MS patients suitable for outcomes analysis.