This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
A middle aged female presents with polyahritis, elevated Rheumatoid factor and ANA levels. Which of the following features will help in differentiating Rheumatoid ahritis from SLE 
Select and explain. 
A. Soft tissue swelling in PIP Joint, B. Juxta-aicular osteoporosis on X ray, C. Aicular erosions on X Ray, D. Elevated ESR
C: Aicular erosions on X Ray
Answer: C: Aicular erosions on X Ray 
Explanation: Answer is C i.e. (Aicular erosions on X ray): SLE is associated with non-erosive ahritis. Presence of aicular erosions on X Ray suggests a diagnosis of' Rheumatoid Ahritis `Erosions on joint X-Rays are rare in SLE; their presence suggests a non-lupus inflammatory ahropathy such as Rheumatoid Ahritis' - Harrison 17th/2077 `SLE may he confused with other connective tissue disease, especially Rheumatoid Ahritis. SLE patients may have positive Rheumatoid Factor. The usual presentation of lupus ahritis is identical to that of Rheumatoid Ahritis, but SLE ahritis is rarely erosive.' - Current Rheumatology 2nd/208