Abstract: A process for differential diagnosis of various rheumatological and arthritic diseases, all of which may yield similar antinuclear antibody test results. The process comprises a continuous sequence of tests on a single serum specimen to minimize and eliminate variations, thus providing accurate results. The process involves drawing a serum from a patient and first performing an antinuclear antibody test which is evaluated. If the evaluation is positive, then the particular type of positive indication is interpreted. If the interpretation reveals peripheral or speckled immunofluorescence, then a diagnosis of active Systemic Lupus Erythematosus (SLE), or mixed connective tissue disease (MCTD) are suggested, and automatically additional confirming tests will be performed as part of the process. These tests are the anti-DNA (Deoxyribonucleic Acid), the anti-ENA (extractable nuclear antigen).