6. 56歲男性患者主訴為眼乾、口乾、兩側腮腺腫脹、及眼皮浮腫有三個月之久。一年前的健康檢查發現serum amylase昇高,腹超檢查發現胰臟頭部腫脹及膽管、膽囊有纖維化。血清學檢查發現:anti-SSA及anti-SSB正常,ANA 1:160 speckled, Schirmer's test: OD 4mm/5min, OS: 6mm/5min. 請問下列的何種檢查對疾病的鑑別診斷最有幫助?
(A) Serum lipase
(B) Sialoscintigraphy
(C) Anti-mitochondrial antibodies
(D) Anti-smooth muscle antibodies
(E) Serum IgG4 level