From what I understand, Anti-Smith AB's are only one of eleven things that Docs look at when diagnosing lupus. The ACR criteria for SLE is that a patient should have at least 4 of the 11 signs/symptoms to consider a lupus diagnosis. So the thing is blood work and symptoms together. This is the way that I understand the process, but you may want to verify that for yourself. Hope this helps.

I Agreed with Lbeezy. Even if your ANA is negative, there are other testings and symptoms that will give you your diagnosis.