The aim of this study was to determine whether estimation ofsialic acid levels, both in the serum and pleural fluid, ofpatients with pleural effusion is ofsignificance in detecting malignant pleural effusions. This study included 50 patients with pleural effusion, 20 patients with malignant effusion (group I) and 30 patients with non malignant effusion (group II). Group II was subdivided into group II-a included 10 patients with tuberculous effusions, group II-b included 10 patients with parapneumonic effusion and group II-c included 10 patients with transudative effusion. Group III of 20 apparently healthy subjects
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as a control group was also included. The mean sialic acid level in the serum of the control group was
6.13 ± 1.87 mg/dl, in the non malignant group it was 10.04 ± 3.18 mg/dl and in the malignant group it
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was 18.85 ± 7.34 mg/dl (P < 0.0(05). The mean sialic acid level in the pleural fluid of group II (non malignant group) was 5.6 ± 2.42 mg/dl while in group I (malignant group) lVas 9./6 ±3.08 mg/dl (P < 0.0005). It can be concluded that, there is significant association between malignancy and raised sialic acid in the serum and pleural fluid, thus estimation of sialic acid level may be helpful as a tumour
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marker in the diagnosis ofmalignant pleural effusion.