Serum cell death biomarkers for prediction of liver fibrosis and poor prognosis in primary biliary cirrhosis

Abstract

The development of simple, noninvasive markers of liver fibrosis is urgently needed for primary biliary cirrhosis (PBC). This study examined the ability of several serum biomarkers of cell death to estimate fibrosis and prognosis in PBC. A cohort of 130 patients with biopsy-proven PBC and 90 healthy subjects were enrolled. We assessed the utility of the M30 ELISA, which detects caspase-cleaved cytokeratin-18 (CK-18) fragments and is representative of apoptotic cell death, as well as the M65 and newly developed M65 Epideath (M65ED) ELISAs, which detect total CK-18 as indicators of overall cell death, in predicting clinically relevant fibrosis stage. All 3 cell death biomarkers were significantly higher in patients with PBC than in healthy controls and were significantly correlated with fibrosis stage. The areas under the receiver operating characteristic curve for the M65 and M65ED assays for differentiation among significant fibrosis, severe fibrosis, and cirrhosis were 0.66 and 0.76, 0.66 and 0.73, and 0.74 and 0.82, respectively. In multivariate analysis, high M65ED (hazard ratio 6.13; 95% confidence interval 1.18-31.69; P = 0.031) and severe fibrosis (hazard ratio 7.45; 95% confidence interval 1.82-30.51; P = 0.005) were independently associated with liver-related death, transplantation, or decompensation. High serum M65ED was also significantly associated with poor outcome in PBC (log-rank test; P = 0.001). Noninvasive cell death biomarkers appear to be clinically useful in predicting fibrosis in PBC. Moreover, the M65ED assay may represent a new surrogate marker of adverse disease outcome.

Fig 1. Correlation of the cell death biomarkers (A) M30, (B) M65, and (C) M65ED with liver fibrosis scores in primary biliary cirrhosis.

Boxes represent the interquartile range (IQR) of the data. The lines across the boxes indicate the median values. Hash marks depict the nearest value within 1.5 times the IQR. Open circles indicate outliers. Detection by M30 (A) and M65 (B) was unable to significantly discriminate between F0-F3 and F4 fibrosis stages but could differentiate between F0-1 and ≥F2 or F0-2 and ≥F3 stages of fibrosis. Estimation using M65ED could significantly discriminate between all fibrosis stages.

Fig 2. Receiver operating characteristic analysis of the 3 cell death biomarkers (M30, M65, and M65ED) for the prediction of (A) significant fibrosis (≥F2), (B) severe fibrosis (≥F3), and (C) cirrhosis (F4).

Fig 3. Cumulative survival rate analyzed using the Kaplan-Meier method according to baseline M65ED levels.

Survival was significantly lower in patients when M65ED level was ≥ 672 U/L (P = 0.001).