This may be attributed to the following reasons: a) the total protein levels in these six patients had decreased to varying degrees, ranging from 35.3 mg to 56.5 mg/L, and a small amount of pleural effusion might have been caused by the decrease in plasma colloid osmotic pressure due to slight hypoproteinemia; b) The CRP levels were elevated in all the six patients, ranging from 21.17.85–60.3 mg/L, thus indicating certain inflammatory reactions. This evidence concerns the gene CRP and Pleural effusion.