Soluble leukocyte selectin in the analysis of pleural effusions

Study objectives: To determine if soluble leukocyte selectin (sL-selectin) levels in serum and pleural fluid (PF) are an inflammatory marker that differentiates pleural effusion transudates from exudates. Design: sL-selectin PF and serum levels were measured in consecutive patients and compared to established criteria. Setting: A tertiary-care military medical center. Patients: One hundred twenty patients undergoing diagnostic or therapeutic thoracentesis. Interventions: PF and serum samples were collected during thoracentesis and analyzed separately for sL-selectin levels. Results were compared with clinical diagnosis and established PF criteria including the criteria of Light et al, cholesterol ratio, total bilirubin ratio, and albumin gradient. Measurements and results: sL-selectin levels in PF and serum were determined in 109 patients. By clinical diagnosis, mean ± SD PF sL-selectin levels were 200.2 ± 124.3 ng/mL in transudates and 496.8 ± 379.2 ng/mL in exudates (p < 0.001). By the criteria of Light et al, mean PF sL-selectin levels were 195.7 ± 105.2 ng/mL in transudates and 448.2 ± 367.6 ng/mL in exudates (p < 0.001). Mean sL-selectin PF to serum ratios were 0.31 ± 0.17 in transudates and 0.72 ± 0.31 in exudates (p < 0.001) by clinical criteria, and 0.31 ± 0.18 in transudates and 0.64 ± 0.33 in exudates (p < 0.001) by the criteria of Light et al. No significant difference was noted with serum sL-selectin levels between groups. Conclusions: sL-selectin is an inflammatory marker that differentiates transudates from exudates in pleural effusions and is a sensitive indicator for PF analysis.