This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunity, Subject name: Pathology
Best marker of SLE? 
Select and explain. 
A. Anti Sm antibodies, B. Anti-ds DNA antibodies, C. Anti-Histone antibodies, D. Anti Ro (SS-A) antibodies
B: Anti-ds DNA antibodies
Answer: B: Anti-ds DNA antibodies 
Explanation: Ans. (b) Anti-ds DNA antibodies(Ref: Harrison 18th/chapter 319)Anti dsDNA is specific for SLE, only in high titers;But still, anti ds DNA is the best marker for SLE because its prevalence in SLE is 70%;Whereas, Anti Sm antibody, which is specific for SLE, but is seen in only 25% patients with SLE