BLOOD TEST DETECTS ANTINUCLEAR ANTIBODIES IN YOUR BLOOD.  
YOUR IMMUNE SYSTEM NORMALLY MAKES ANTIBODIES TO HELP YOU FIGHT/DESTROYS FOREIGN SUBSTANCES SUCH AS BACTERIA AND VIRUS. 
IN CONTRAST, ANTINUCLEAR ANTIBODIES OFTEN ATTACK YOUR BODY’S OWN TISSUE, SPECIFICALLY TARGETING EACH CELL’S NUCLEUS. MANY RHEUMATIC DISEASES HAVE SIMILAR SIGNS AND SYMPTOMS (JOINT PAIN, FATIGUE AND FEVER). “ANA” TEST CAN RULE OUT SOME POSSIBLE DISEASE