What is the significance of a positive ANA in a patient with chronic polyarticular symptoms?
A patient with polyarthralgia or polyarthritis who has a significantly elevated ANA titer (≥1:320) has an elevated risk of one of the following diseases: SLE (including drug-induced lupus), RA, Sjögren’s syndrome, polymyositis, systemic sclerosis, or mixed connective tissue disease. The history and physical examination should be directed toward the clinical findings commonly seen in these diseases. A careful medication history may reveal that the patient has received drugs that can cause drug-induced lupus (see Chapter 17 : Drug-Induced Lupus). An absence of objective findings on exam, coupled with lack of end-organ dysfunction through laboratory evaluation, is reassuring evidence against a rheumatic etiology. It is important to note that a positive ANA is a feature of several other chronic diseases other than those listed earlier and can also be found in normal healthy individuals, although usually in low titer
