Feasibility and validity were demonstrated of an online case–control study using the prototype of recent-onset systemic lupus erythematosus

ObjectiveTo test the feasibility and validity of the online case–control study design through the empirical deployment of a prototype study of recent-onset systemic lupus erythematosus (SLE).Study Design and SettingWe conducted an Internet-based case–control study of SLE during 2003–2005. The source population comprised Google users searching on medical key terms, solicited using sponsored links. Cases fulfilled a self-administered algorithm for SLE diagnosed within 5 years. A subset underwent confirmation by medical record review. Controls were matched to cases using a propensity score.ResultsFour hundred and two cases and 693 control applicants finished the questionnaires, yielding 389 matched case–control pairs. Eighty-two percentage of the records documented a clinical diagnosis of SLE, and 61% documented ≥4 American College of Rheumatology criteria for SLE. Control applicants resembled Internet users, with the exceptions of comprising more women (86% vs. 52%) and fewer minority individuals (e.g., 5% vs. 9% for African-Americans). There was a broad representation of clinical manifestations. SLE was associated with miscarriage (odds ratio [OR] = 3.0, 95% confidence interval [CI] = 2.0–4.7), allergy to sulfonamides (OR = 2.2, CI = 1.5–3.2), hives (OR = 1.9, CI = 1.4–2.5), and shingles (OR = 2.3, CI = 1.4–3.7).ConclusionIt is possible to perform case–control studies over the Internet using an internally valid design, obtain reliable information from participants, and confirm established associations.