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12 PROGNOSTIC VALUE OF SERUM SODIUM CONCENTRATION AND MODEL FOR END-STAGE LIVER DISEASE IN PATIENTS ON THE LIVER TRANSPLANTATION WAITING LIST

Background/Aim Model for end stage liver disease (MELD), an accurate predictor of survival in patients with end stage liver disease (ESLD), has been used to prioritize livers for transplantation (OLT). Hyponatremia, a common complication of ESLD, is also considered a poor prognostic indicator. However, there are few data on how much prognostic value serum sodium (Na+) adds to MELD in predicting survival among patients with ESLD awaiting OLT. We assess the prognostic value of Na+ in conjunction with MELD in predicting survival among patients awaiting OLT. Methods This was a retrospective analysis of a prospective cohort consisting of all adult patients with ESLD registered on the waiting list at our institution from the preMELD era (1990-1999). Acute liver disease and hepatic malignancies were excluded. Laboratory data at the time of listing for OLT were obtained from a computerized laboratory database. The outcome of interest was death on the waiting list within 30, 60, and 90-days of listing. Odds ratios (OR) and receiver operator characteristic curves (ROC) were generated using multivariate logistic regression. Additionally, these same data were also analyzed using Cox regression competing risks. Results 861 patients met inclusion criteria with mean age of 50 (SD = 10) of whom 55% were male. Median MELD at listing was 15 (interquartile range, IQR: 11-19). Median Na+ was 137 mEq/L (IQR: 134-140). Using logistic regression, MELD was significantly associated with increased mortality on the waiting list at 30 and 90-days, OR = 1.15 and 1.23, respectively (p<0.001). Adjusting for MELD, decreasing Na+ concentrations conferred increased risk of death at 90-days only, with OR for Na+ = 0.9 (p<0.01). Dichotomizing Na+ as low and high (< 126 and ≥ 126 mEq/L, respectively) revealed that low Na+, adjusting for MELD, was significantly associated with mortality at 90-days only, OR for Na+ = 4.28 (p = 0.02). Finally, adding Na+ to MELD changes little in the ROC curves at 90-days (c-statistic for MELD = 0.88; c-statistic for MELD plus Na+ = 0.89). However, competing risk analysis revealed that low Na+ does provide important prognostic value for patients on the liver transplant waiting list, with a Na+<126 mEq/L being equivalent to ˜ 8-10 additional MELD points. Conclusion In a simple alive/dead analysis (logistic regression), serum Na+ does not appear to add a measurable gain to the prognostic value of MELD. However, in a more appropriate competing risk analysis, serum Na+ is a significant predictor of death in patients awaiting liver transplantation. Therefore, the addition of sodium to MELD in this group of patients may help optimize allocation.