Acute-phase proteins as indicators of bacterial infection in patients with cirrhosis

Cirrhosis is associated with elevated levels of acute-phase proteins (APP), irrespective of the presence of infection. This condition limits the clinical application of APP determination in cirrhotic patients with bacterial infections.

To weigh the diagnostic value of several APP in cirrhotics with or without bacterial infection, and to correlate them with the clinical outcome.

We investigated 88 consecutive cirrhotic patients (67 males, 21 females; range 28-85 years) with mean age (SD) 58.9 (13.8) on admission, according to a standard protocol for infection. We measured the following APP: C-reactive protein (CRP), fibrinogen (FIB), haptoglobin (Hpt), ferritin (Fer), beta2-microglobulin (beta2-mg), C3, C4 and C1 inhibitor.

From the 88 patients, 19 (21.6%) had documented infection at the entry based on clinical, radiological and microbiological data. This group of patients did not differ in basic demographics from those without infection. CRP [17.5 (20.7) vs 77.1 (43.9), P<0.001], beta2-mg [4.4 (4.1) vs 5.6 (2.2), P<0.001] and ferritin [461.2 (776.4) vs 825.8 (870), P=0.03] were significantly higher in infection, whereas C3 was significantly lower. No significant differences were noted in the remaining APP levels between the two groups. After receiver operating characteristic curves were fitted, CRP was the best diagnostic test for infection (area under the curve 0.91), followed by beta2-mg, ferritin, FIB, C1 inhibitor, C4, Hpt and C3.

Serum CRP is the best test, among the examined APP, to discriminate bacterial infection in cirrhotics. A cut-off value of >55.8 mg/L has high sensitivity (79%) and specificity (96%), with the best diagnostic accuracy (92%).