How to distinguish pleural effusion from transudate or exudate

Transudate and exudate two kinds of pleural effusion, its nature has obvious difference. First, transudate is usually due to the patient's albumin index decreased, vascular internal osmotic pressure increased and other factors, mostly clear transparent or light yellow liquid. Second, exudate is generally due to bacterial infection, malignant tumor and other diseases caused by the liquid is purulent, and can present yellow, green and other abnormal colors.