Abstract: Objective: To investigated the role of transthyretin (TTR) level and its modification in serum and pleural fluid (PF) for diagnosis of infectious lung disease. Methods: (1) The level of Total protein (TP), albumin (ALB), triglycerides (TG), cholesterol (Cho), apolipoprotein A (Apo A), apolipoprotein B (Apo B ), lactate dehydrogenase (LDH), adenosine deaminase (ADA), glucose (GLU), and transthyretin protein (TTR) etc. were detected in serum and PF samples.(2) Chemically modified type and proportion of TTR proteins was analyzed by matrix-assisted laser ionization time of flight mass spectrometry (MALDI-TOF-MS). Results: (1) 8 components were significantly lower in PF than in serum, reduced order as follow: TG, Cho, TTR, ApoA, ApoB, TP, Alb and GLU , while the ADA was increased only, and LDH was no statistical differences; (2) Among protein indexs, TTR is the most significantly reduced one; (3) 2 types of modified TTR were detected in PF and serum of patients with infectious lung disease, while contrast with the healthy control group ,no cysgly-TTR was present. Conclusions: The cysgly-TTR was disappeared in both PF and serum, indicating that TTR modification may be an assistant for lung infection diagnosis.

Key words: lung infection, transthyretin, diagnosis, pleural effusion, serum