Conjugated bilirubin , a liver function biomarker, proved to be a relatively powerful indicator of in-hospital and long-term adverse prognosis of infective endocarditis (IE), according to study results published in the European Journal of Clinical Microbiology & Infectious Diseases.
To investigate the potential link between conjugated bilirubin and adverse prognosis in patients with IE, 1010 patients with IE were enrolled between January 2009 and July 2015. Researchers divided patients into 2 groups according to their conjugated bilirubin level at admission: normal (≤7; n=820) and elevated (>7; n=190). They performed multivariate analysis to confirm whether conjugated bilirubin was, in fact, an independent risk factor for adverse outcomes.
In patients with increased conjugated bilirubin, in-hospital mortality (5% vs 22.1%, P <.001) and major adverse cardiac events (16.8% vs 36.3%, P <.001) were significantly higher. Conjugate bilirubin also had more predictive power than total bilirubin in predicting in hospital death (area under the curve 0.715 vs 0.674; P =.01) and elevated conjugated bilirubin was an independent predictor of in-hospital death (adjusted odds ratio, 2.62; 95% CI, 1.4-4.91, P =.003). Higher mortality was also independently associated with conjugated bilirubin (increment 1 μg/dL). In addition, according to Kaplan-Meier curves, patients with elevated conjugated bilirubin were associated with a higher cumulative rate of long-term death (log-rank, 21.47; P <.001).
Investigators also found a possible J-shaped relationship between conjugated bilirubin and in-hospital events; however, this could not be confirmed because of the small sample size. Further, the study was limited, as it was a retrospective analysis based on prospectively collected data, and investigators reported that residual confounding factors possibly affected the mortality risk despite the use of multivariate logistic regression. Another possible limitation is that the researchers did not measure conjugated bilirubin dynamically, meaning the prognostic value of change in conjugated bilirubin level for adverse outcomes was unclear.
The study does concluded that in patients with IE, elevated conjugated bilirubin was independently associated with higher in-hospital and long-term death rates, and it was a stronger predictor of in-hospital mortality than total bilirubin. Investigators, therefore, highlighted that “assessment of [conjugated bilirubin] levels could be a novel approach for risk evaluation in IE and potentially helpful to identify those at high risk of adverse outcomes.”
Wei XB, Wang Y, Liu YH, Huang JL, Yu DQ, Chen JY. Effect of conjugated bilirubin on clinical outcomes in infective endocarditis [published online August 19 2019]. Eur J Clin Microbiol Infect Dis. doi:10.1007/s10096-019-03670-4