This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Scleroderma, Subject name: Medicine
Screening test for sclerodema? 
Select and explain. 
A. Anti-nuclear antibody, B. U l- Ribonucleoprotein antibody, C. Anti- L.K.M antibody, D. Anti- topoisomerase antibody
A: Anti-nuclear antibody
Answer: A: Anti-nuclear antibody 
Explanation: Anti-nuclear antibody- ANA is the screening method of choice for systemic rheumatic disease such as systemic lupus ehyematosus (SLE), mixed connective tissue disease, Sjogren syndrome, scleroderma, CREST syndrome, rheumatoid ahritis, polymyositis, and dermatomyositis.