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Comparative Study
. 2008 Sep 4;359(10):1018-26.
doi: 10.1056/NEJMoa0801209.

Hyponatremia and Mortality Among Patients on the Liver-Transplant Waiting List

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Free PMC article
Comparative Study

Hyponatremia and Mortality Among Patients on the Liver-Transplant Waiting List

W Ray Kim et al. N Engl J Med. .
Free PMC article

Abstract

Background: Under the current liver-transplantation policy, donor organs are offered to patients with the highest risk of death.

Methods: Using data derived from all adult candidates for primary liver transplantation who were registered with the Organ Procurement and Transplantation Network in 2005 and 2006, we developed and validated a multivariable survival model to predict mortality at 90 days after registration. The predictor variable was the Model for End-Stage Liver Disease (MELD) score with and without the addition of the serum sodium concentration. The MELD score (on a scale of 6 to 40, with higher values indicating more severe disease) is calculated on the basis of the serum bilirubin and creatinine concentrations and the international normalized ratio for the prothrombin time.

Results: In 2005, there were 6769 registrants, including 1781 who underwent liver transplantation and 422 who died within 90 days after registration on the waiting list. Both the MELD score and the serum sodium concentration were significantly associated with mortality (hazard ratio for death, 1.21 per MELD point and 1.05 per 1-unit decrease in the serum sodium concentration for values between 125 and 140 mmol per liter; P<0.001 for both variables). Furthermore, a significant interaction was found between the MELD score and the serum sodium concentration, indicating that the effect of the serum sodium concentration was greater in patients with a low MELD score. When applied to the data from 2006, when 477 patients died within 3 months after registration on the waiting list, the combination of the MELD score and the serum sodium concentration was considerably higher than the MELD score alone in 32 patients who died (7%). Thus, assignment of priority according to the MELD score combined with the serum sodium concentration might have resulted in transplantation and prevented death.

Conclusions: This population-wide study shows that the MELD score and the serum sodium concentration are important predictors of survival among candidates for liver transplantation.

Conflict of interest statement

No potential conflict of interest relevant to this article was reported.

Figures

Figure 1
Figure 1
Serum Sodium Concentration and the Relative Risk of Death after Adjustment for the MELD Score.
Figure 2
Figure 2. Computation of the MELDNa Score on the Basis of the MELD Score and the Serum Sodium Concentration
The graph shows the allocation points a patient would receive for a given Model for End-Stage Liver Disease (MELD) score and serum sodium concentration. Boxes of the same color share the same allocation points.
Figure 3
Figure 3. Observed and Predicted Probability of Death at 90 Days
Panel A shows the observed probability of death for the 2005 data and the predicted probability according to the Model for End-Stage Liver Disease–sodium (MELDNa) score in 10 groups (deciles) of patients. Panel B shows the observed probability of death for the 2006 data and the predicted probability according to the MELDNa and MELD scores in 10 groups (deciles) of patients.
Figure 4
Figure 4. Distribution of MELD and MELDNa Scores among the 477 Patients Who Died while on the Waiting List, 2006
Dark orange cells represent patients in whom the Model for End-Stage Liver Disease (MELD) score and the MELDNa score were similar. Light orange cells correspond to the 110 patients with a MELDNa score that was higher than the MELD score and in a range that might have made an organ available for transplantation. In 2006, the probability of receiving a liver transplant increased from 18.5% for a patient with a MELD score from 10 to 19 to 58.4% for a patient with a MELD score from 20 to 29 and to 70.4% for a patient with a MELD score from 30 to 39. If the MELDNa score had been used for liver allocation, the expected number of transplantations would have increased by 32, as calculated with the following formula: 67 × (58.4% − 18.5%) + 43 × (70.4% − 58.4%). Thus, 7% of deaths (32 of 477) that occurred within 3 months after registration on the waiting list might have been prevented.

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