Autoimmune diseases may involve nearly any organ and are characterized by abnormal activation or response of certain cells. Evidence suggests that farm work, exposure to silica from farming activities and exposure to pesticides may contribute to the development of autoimmune disease. Associations between autoimmune diseases and farming, however, have not been extensively investigated, and exposure data in the currently available studies are extremely limited.

One of the major challenges in conducting population-based research on autoimmune diseases is case ascertainment. Self-report of previous diagnosis has proven to be unreliable. This protocol outlines a strategy to confirm self-reported diagnoses of systemic autoimmune diseases (rheumatoid arthritis, systemic lupus erythematosus, scleroderma, and Sjogren syndrome) within the Agricultural Health Study group (AHS; a group of licensed pesticide applicators and spouses who completed a questionnaire). The confirmed cases will constitute a refined case group to allow analyses of pesticides and other farming-related exposures as possible risk factors for these diseases using data that have already been collected.

Subjects will be selected from participants in the AHS who reported one of the diseases being studied. A short telephone interview will be conducted with participants, who will be requested to provide written consent for review of information from medical records. To confirm the self-diagnosis, participants' physicians will be contacted. Specific information will be requested in the form of a checklist. Responses will be reviewed for evidence of diagnosis and classified as confirmed, probable, physician-diagnosed, or unconfirmed.

Secondary objectives of this study are to:

• assess the correct interpretation of conflicting self-reports that are provided at two different times.
• evaluate the usefulness of specific questions that could potentially be used in future studies to validate self-reported cases of rheumatoid arthritis in men.