Interleukin-6: an early marker of bacterial infection in decompensated cirrhosis

Fifty-seven patients with decompensated cirrhosis were studied prospectively to assess the sensitivity and specificity of early clinical or biological signs of bacterial infection. Among them, 19 had proven infection on admission (7 spontaneous bacterial peritonitis, 5 bacteraemia, 3 urinary tract infections, 2 pneumonia, 1 dental abscess and 1 cholangitis). Fever, polymorphonuclear cell count, fibrinogen and C-reactive protein levels were found to be of little or no help in diagnosing bacterial infection on admission. Interleukin-6 plasma levels were, however, significantly different between infected (median: 1386 pg/ml, range: 237-20,000) and non-infected patients (median: 34 pg/ml, range: 0-4500, p < 0.00001). Levels above 200 pg/ml were always found in infected patients, giving a sensitivity of 100% and a specificity of 74%. C-reactive protein correlated weakly with interleukin-6 levels, indicating a defective acute-phase response in cirrhosis. Tumor necrosis factor alpha plasma levels were less sensitive (95%) and specific (68%) for the diagnosis of bacterial infection at a threshold of 50 pg/ml, but were more closely related to a poor patient outcome. In decompensated cirrhosis, interleukin-6 plasma levels on admission provided the most sensitive and specific tool for the diagnosis of bacterial infection.