Clinical evaluation Clinical factors predicting the diagnosis of<unk> s are symptoms lasting more than 1 month and the absence of fever. Imaging This is needed to confirm the presence of a<unk><unk> . Chest radiograph is usually performed first and may demonstrate an underlying lung cancer as well as the<unk><unk> . Ultrasound has a sensitivity of 73% and specificity of 100% at distinguishing<unk> s from other causes of<unk><unk> , based on the presence of visible<unk>  metastases,<unk>  thickening greater than 1 cm,<unk>  nodularity, diaphragmatic thickening measuring greater than 7mm and an echogenic swirling pattern visible in the<unk>  fluid. Biochemical analysis<unk> s are exudates. A low<unk>  fluid pH is associated with poorer survival and reduced pleurodesis efficacy. Histopathology<unk>  fluid cytology is positive in 60% of cases. However, in the remaining cases,<unk>  biopsy is required. Image guided biopsy and thoracoscopy have largely replaced blind biopsy due to their greater sensitivity and safety profile. CT guided biopsy has a sensitivity of 87% compared to Abrams' needle biopsy, which has a sensitivity of 47%. Biomarkers Identification of<unk>  fluid biomarkers to distinguish<unk> s from other causes of exudative<unk> s would help diagnosis. Biomarkers that have been shown to be raised in<unk> s compared to benign disease include vascular endothelial growth factor (VEGF), endostatin, matrix metalloproteinases and tumour markers such as carcinoembryonic antigen.<unk>  fluid mesothelin has a sensitivity of 71%, greater than that of cytology, and a specificity of 89% for the diagnosis of<unk>  mesothelioma.
Malignant pleural effusion
Pleural empyema
Lung abscess
Atypical pneumonia
Lobar pneumonia
Viral pneumonia
Parapneumonic effusion
Pneumonia of unknown etiology 