How to diagnose procainamide induced systemic lupus.?

It might be hard to differentiate drug induced lupus and systemic lupus , but the history is very important . It can take some time to develop drug induced lupus but generally the symptoms are less severe, sparing the major organs .Most important,the skin rash and other signs and symptoms clear up after stopping the medicine..Antihistone antibodies are helpful in diagnosing drug induced lupus.