Pleural SC5b-9: A test for identifying complicated parapneumonic effusions

Background and Objective: We have tested whether the complement activation products SC5b-9 and C3a-desArg are useful to distinguish complicated (CPE) from uncomplicated parapneumonic effusions (UPE). Design: A total of 66 pat ients were enrolled in the study: 5 with empyema, 19 with CPE, 12 with UPE, and 30 transudates who served as controls. SC5b-9 and C3a-desArg were meas ured by commercial ELISA tests, and their performances were evaluated using receiver operating characteristic (ROC) analysis. Results: Patients with C PE had higher mean levels of pleural SC5b-9 (8,218 mu g/l) and C3a-desArg ( 8,790 mu g/l) than those with UPE (2,227 and 3,772 mu g/l, respectively; p < 0.0001), whereas concentrations in the latter were comparable with contro ls for the SC5b-9 test. Empyemas had a wide range of pleural complement act ivation product values. Pleural SC5b-9 and C3a-desArg showed very high diag nostic accuracy in the diagnosis CPE (90.3 and 77.8%, respectively) when co rresponding cutoff points of 2,000 and 4,000 mu g/l were used. In a stepwis e logistic regression analysis, the combination of SC5b-9 greater than or e qual to 2,000 mu g/l, LDH greater than or equal to 1,000 U/l and a pleural polymorphonuclear percentage greater than or equal to 85% provided the high est discriminative power for the diagnosis of CPE (area under ROC curve 0.9 7). Conclusion: This pilot study suggests that measurement of pleural SC5b- 9 can be useful in the workup of patients with a parapneumonic effusion in order to differentiate CPE from UPE. Copyright (C) 2000 S. Karger AG, Basel .