Pleural SC5b-9: a test for identifying complicated parapneumonic effusions.
BACKGROUND AND OBJECTIVES We have tested whether the complement activation products SC5b-9 and C3a-desArg are useful to distinguish complicated (CPE) from uncomplicated parapneumonic effusions (UPE).


METHODS
A total of 66 patients 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 measured by commercial ELISA tests, and their performances were evaluated using receiver operating characteristic (ROC) analysis.


RESULTS
Patients with CPE had higher mean levels of pleural SC5b-9 (8,218 microg/l) and C3a-desArg (8,790 microg/l) than those with UPE (2,227 and 3,772 microg/l, respectively; p < 0.0001), whereas concentrations in the latter were comparable with controls for the SC5b-9 test. Empyemas had a wide range of pleural complement activation product values. Pleural SC5b-9 and C3a-desArg showed very high diagnostic accuracy in the diagnosis CPE (90.3 and 77.8%, respectively) when corresponding cutoff points of 2,000 and 4,000 microg/l were used. In a stepwise logistic regression analysis, the combination of SC5b-9 >/=2,000 microg/l, LDH >/=1,000 U/l and a pleural polymorphonuclear percentage >/=85% provided the highest discriminative power for the diagnosis of CPE (area under ROC curve 0.97).


CONCLUSIONS
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.
Vives
M
M
Department of Internal Medicine, University Hospital Arnau de Vilanova, University of Lleida, Spain. jporcelp@medynet.com
Porcel
J M
JM
Gázquez
I
I
Pérez
B
B
Rubio
M
M
D000328:Adult; D000368:Aged; D015926:Complement C3a / Q000031:analogs & derivatives* / Q000032:analysis; D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins / Q000032:analysis*; D005260:Female; D006023:Glycoproteins / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D010994:Pleura / Q000737:chemistry*; D010996:Pleural Effusion / Q000175:diagnosis* / Q000209:etiology*; D018410:Pneumonia, Bacterial / Q000150:complications*
D015938:Complement Membrane Attack Complex; D006023:Glycoproteins; C047610:SC5b-9 protein complex; C044541:complement C3a, des-Arg-(77)-; D015926:Complement C3a; D003165:Complement System Proteins