This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of pituitary gland, Subject name: Medicine
Which of these tests is the first to be performed in a patient with the following presentation? 
Select and explain. 
A. ABG sampling, B. IGF- 1 levels, C. RA factor, D. HLA- B27 levels
B: IGF- 1 levels
Answer: B: IGF- 1 levels 
Explanation: IMAGE : SPADE LIKE DEFORMITY OF HANDS: Seen in ACROMEGALY Screening test done: IGF -1 IOC: Glucose challenge test (GCT) Treatment: Surgery (Transphenoidal Resection) If recurrence seen: PEGVISOMANT