Feasibility and validity were demonstrated of an online case-control study using the prototype of recent-onset systemic lupus erythematosus.
OBJECTIVE
To 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 SETTING
We 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.


RESULTS
Four 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 >or=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).


CONCLUSION
It is possible to perform case-control studies over the Internet using an internally valid design, obtain reliable information from participants, and confirm established associations.