Objective To assess the clinical value of pentraxin-3 (PTX-3) in diagnosis and survey of therapeutic effect for lung cancer. Methods The serum level of PTX-3,carcinoembryonic antigen (CEA),cytokeratin 19 fragment (CYFRA 21-1) were measured in 802 patients with lung cancer,462 with benign lung diseases and 522 healthy controls from multiple research centers,using ELISA and electrochemiluminescent assays.The clinical value of PTX-3 was assessed by comparing the area under receiver characteristic curves (AUC) with CEA and CYFRA21-1.The optimum cutoff value for diagnosis of lung cancer was investigated by maximizing the sum of sensitivity and specificity.By following-up,the serum level of PTX-3 was measured at 3 day,7 day,and 14 day in 61 lung cancer patients after surgical resection of lung cancer. Results In test group and validation,the serum levels of PTX-3 (g/L) are significantly higher in lung cancer group[9.21 (6.13-12.80),10.4 (5.54-13.11)] than in benign lung diseases[5.28 (3.42-8.53),6.52 (3.84-7.89)]and in healthy controls[2.18 (0.54-5.44),2.44 (0.67-5.87)],[Z=8.161,14.118,(test group,all P<0.05) ;Z=9.832,17.595 (validation group,all P<0.05)].ROC curve showed the optimal cut-off values for PTX-3 was 8.03 g/L[AUC of 0.831,with a sensitivity of 76.1% and specificity of 75.2% in the test cohort; 0.828,71.3%,89.2% in the validation cohort].Similar results were noted for early-stage lung cancer[0.764,79.1%,and 62.2% in the test cohort; 0.744,71.3%,and 69.6% in the validation].In the diagnosis of early-stage lung,the AUCand sensitivity and specificity of PTX-3 were 79.1%,0.764,71.3% (test group),and 75.2%,89.2%,0.824 (validation group) significantly higher in these patients than CEA and CYFRA21-1.In small cell lung cancer,PTX-3 and NSE shared similar AUC differentiating LC from benign lung diseases and health controls.In following-up 61 lung cancer patients,PTX-3 levels before surgical resection of tumours[11.12 (9.12-12.59)] was significant high than following 3 day after surgery (Z=4.32,P<0.01),and 14 day (5.12±2.54) vs.7 day (7.13±3.42)(t=2.143,P=0.023).The correlation between PTX-3 and CRP in LC,benign lung diseases,health control was 0.364,0.592,0.512 (all P<0.05). Conclusion Serum PTX-3 is a valuable biomarker of lung cancer and early-stage lung cancer with high sensitivity and specificity and improved identification of patients with lung cancer from those with non-malignant chronic lung diseases.(Chin J Lab Med,2013,36:997-1001) Key words: Lung neoplasms; Serum amyloid P-component; C-reactive protein; Tumor markers; biological; Prognosis