[Chinese expert consensus on diagnosis of pleural effusion].

Pleural effusion(PE) is a common medical problem with various causes. The differential diagnosis for PE is often challenging. This consensus was generated by members of the academic group of the pleural and mediastinal diseases(preparatory) of Chinese Thoracic Society and some external experts. The members convened in virtual meetings and conducted an extensive literature investigation and assessed the quality of the evidence using a modified grading of recommendations assessment, development, and evaluation(GRADE) approach. This consensus included three chapters: the initial evaluation of PE, the diagnosis of PE with common causes, and the diagnosis of PE with uncommon causes.The main recommendations of Chapter Ⅰ were as follows:(1) For patients suspected of PE according to medical history and clinical manifestations, thoracic CT or ultrasound is recommended to confirm the presence or absence of PE.(2) Ultrasound-guided thoracentesis is recommended when available. Recommended tests for all sampled pleural effeusions include total protein, lactate dehydrogenase (LDH), adenosine deaminase (ADA), differential cell count, and cytological examination.(3) It is recommended to use Light's criteria to distinguish exudate and transudate. When PE is classified to be exudates with heart failure, it is recommended to detect N-terminal pro-brain natriuretic peptide of PE or serum-pleural fluid albumin gradient to assist the judgment.(4) Pleural biopsy is recommended for patients for whom the causes of PE cannot be identified by the detection of PE samples, and CT or ultrasound-guided pleural biopsy is more accurate. Thoracoscopy is recommended for patients whose etiology cannot be identified by laboratory tests of PE and/or pleural biopsy histopathology.The main recommendations of Chapter Ⅱ were as follows:(1)It is suggested to obtain more samples or use immunocytochemistry to assist the diagnosis and cell typing when initial cytopathology examination shows atypical cells, suspicious malignant or malignant cells. (2) Liquid medium for Mycobacterium tuberculosis culture is recommended to improve the positive rate. Molecular diagnosis (nucleic acid amplification or Xpert MTB/RIF) is recommended when tuberculous PE is suspected. For suspected tuberculous PE where the examination of PE is inconclusive. CT or ultrasound-guided pleural biopsy or thoracoscopy is recommended to obtain pleural tissue for acid-fast staining, Mycobacterium tuberculosis nucleic acid amplification and culture.(3)C-reactive protein (CRP) of PE is recommended to distinguish uncomplicated PPE from complicated PPE. It is suggested to inoculate pleural effusion into blood culture bottles or culturing specimens from ultrasound-guided pleural biopsy to increase the positive rate.The main recommendations of Chapter Ⅲ were as follows:(1) It is recommended to comprehensively analyze the patients' medical history, clinical manifestations, effusion characteristics, and biopsy pathological results to indentify uncommon causes.(2) It is recommended to detect the presence of chylomicrons or cholesterol crystals, with testing of the levels of triglyceride and cholesterol in PE for clinical suspicion of chylothorax or pseudochylothorax. (3) PE may be the result of a combination of various causes, and it is recommended to screen factors such as heart failure, hypoalbuminemia, and thoracic infection for critical patients.(4) For patients with PE whose cause has not been identified by thoracoscopic pleural biopsy, close follow-up for at least 2 years is recommended to exclude malignant diseases.胸腔积液是多种疾病常见的并发症，其病因诊断具有挑战性。中华医学会呼吸病学分会胸膜与纵隔疾病学组（筹）组织专家，充分评估了胸腔积液诊断领域最新的研究结果，基于GRADE证据分级的原则，经过多次会议讨论和修订，最终形成了胸腔积液诊断的专家共识。本共识分为三章：胸腔积液的评估和检测、常见病因胸腔积液的诊断、其他类型胸腔积液的诊断。第一章主要推荐意见如下：（1）根据病史和临床表现怀疑为胸腔积液的患者，推荐行胸部CT和（或）胸腔超声检查明确有无胸腔积液。（2）有条件情况下，推荐在超声引导下行胸腔穿刺。诊断性胸腔穿刺，建议至少检测胸腔积液总蛋白、乳酸脱氢酶、腺苷脱氨酶、细胞分类计数和细胞病理。（3）建议用Light标准来区分渗出液和漏出液；部分漏出液经Light标准可能被误判为渗出液；如果存在心脏疾病，而胸腔积液判断为渗出液，建议检测胸腔积液N-端脑钠肽前体或血清-胸腔积液白蛋白梯度协助判断。（4）针对胸腔积液样本检测未能明确病因的患者，推荐行胸膜活检，CT或超声引导下胸膜活检准确性更高。经胸腔积液实验室检测和（或）胸膜活检未能明确病因者，建议行胸腔镜检查。第二章主要推荐意见如下：（1）胸腔积液细胞病理显示为异型细胞、可疑恶性或恶性细胞，建议获取更多样本或通过免疫细胞化学协助确诊及分型。（2）建议用液体培养基进行结核分枝杆菌（MTB）培养以提高阳性率。推荐在疑诊结核性胸腔积液时进行分子诊断（核酸扩增或Xpert MTB/RIF）。疑诊结核性胸腔积液而胸腔积液检查未能确诊者，推荐行CT或超声引导下胸膜活检或胸腔镜获取胸膜组织行抗酸染色、结核分枝杆菌核酸扩增和培养。（3）推荐检测胸腔积液C反应蛋白协助鉴别非复杂性肺炎旁胸腔积液（PPE）和复杂性PPE。对PPE和脓胸患者，建议将胸腔积液接种到血液培养瓶中，或将超声引导下胸膜活检的标本进行培养，提高培养阳性率。第三章主要推荐意见如下：（1）如果胸腔积液不能用常见病因解释，建议综合分析患者的病史、临床表现、积液特征和活检病理结果等，以排查少见和罕见病因。（2）临床疑诊乳糜胸或假性乳糜胸，推荐检测胸腔积液中是否存在乳糜微粒或胆固醇晶体，并检测胸腔积液甘油三酯和胆固醇水平。（3）胸腔积液可能是多种病因共同作用的结果，对伴胸腔积液的重症患者，建议排查心力衰竭、低蛋白血症、胸腔感染等因素。（4）对于经胸腔镜胸膜活检仍未明确病因的胸腔积液患者，建议密切随访至少2年以排除恶性疾病。.