In order to be diagnosed with lupus, certain criteria must be met. Previously diagnosis was based on having four out of the eleven criteria which included symptoms such as malar rash and arthritis, as well as lab tests such as anti-double stranded DNA. You could also be diagnosed based on a kidney biopsy showing nephritis plus one clinical criterion (oral ulceration) and one immunologic criterion (ANA).
As of 2019, there is a new classification system according to the American College of Rheumatology and the European League Against Rheumatism. In this system, a person is required to have a positive ANA. Remaining criteria are given a weighted number. In order for the disease to be classified as lupus, the criterion must be greater than or equal to 10. Here is a screenshot of the table taken off the American College of Rheumatology’s website:
There is also a newer test called AVISE CTD that tests for lupus as well as other autoimmune diseases. Hope this helps clarifies the diagnostic process. Please share your diagnosis story!
For further information, check out The American College of Rheumatology.