MELD Na Score

MELD Na explained

The MELD and the MELD Na determine 3-month mortality risk in patients with serious liver conditions, such as cirrhosis.

The scores are also used by the OTPN in the evaluation of patients in which cirrhosis is caused by factors that are not reversible and transplant is the only solution.

The two models are also addressed to patients who:

• Underwent transjugular intrahepatic portosystemic shunt (TIPS);
• Are diagnosed with cirrhosis and are about to undergo non-transpant surgical procedures;
• Suffer from acute alcoholic hepatitis;
• Suffer from acute variceal haemorrhage.

The MELD Na adds the sodium determination to the variables of the original Model of End Stage Liver Disease. The following table introduces the variables used in the calculation of the score:

The four laboratory results should not be older than 48 hours. In addition to the above, the score also accounts for hemodialysis frequency (twice in past week).

The two equations used are the following:

MELD Score = 10 x [(0.957 x ln(Creatinine)) + (0.378 x ln(Bilirubin)) + (1.12 x ln(INR))] + 6.43

MELD Na = MELD − Na − [0.025 × MELD × (140 − Na)] + 140

In cirrhosis, hyponatremia indicates solute-free water retention and is an indirect marker of portal hypertension. Hyponatremia is in general considered a predictor of early mortality, thus why, the addition of sodium to the MELD score, increases its accuracy in predicting 3-month mortality.

A decrease in serum sodium of one unit (when the change is in the range 120-135 mEq/L) corresponds to a 12% increase in mortality risk in the following 3 months.

The MELD Na model has several limitations:

• Not enough relevant validation;
• The model does not account for unrelated sodium changes;*
• There is no adaptation of the score in respect to INR values of patients under anticoagulation therapy because of portal vein thrombosis;
• Survival may not be accurately predicted in 15-20% of cirrhotic patients, so the score is not perfectly universal.

* Sodium changes may be caused by factors unrelated to cirrhosis severity, such as diuretic use or intravenous administration of hypotonic fluids.

MELD exclusions

In 2006, the MELD Exception Study Group and Conference (MESSAGE) created the MELD Exception Guidelines that highlight the conditions in which the formula does not accurately predict mortality:

• Hepatocellular carcinoma (HCC) with one lesion between 2 - 5 cm or two to three lesions <3 cm, but no vascular invasion or extrahepatic disease;
• Hepatopulmonary syndrome with P_aO₂ <60 mmHg on room air;
• Portopulmonary hypertension, with mean pulmonary artery pressure (mPAP) >25 mmHg at rest but maintained <35 mmHg with treatment;
• Hepatic artery thrombosis 7–14 days post-liver transplantation;
• Primary hyperoxaluria with evidence of alanine glyoxylate aminotransferase deficiency;
• Familial amyloid polyneuropathy;
• Hilar cholangiocarcinoma;
• Cystic fibrosis with FEV₁ <40%.

The above conditions are automatically assigned a MELD Score of 22 (28 in case of hyperoxaluria). A 10% increase in score should be accounted for, every 3 months from diagnosis.

Result interpretation

The United Network for Organ Sharing (UNOS) uses the MELD scores to prioritize patients with severe cirrhosis for organ transplant.

The most common met range of scores is between 6 and 40 but extremes can become apparent.

The table below summarizes the 3-month mortality risk, according to MELD (MELD Na) scores:

About the study

The original Model for End Stage Liver Disease was created by Kamath et al. in 2001. As per the January 2016 OTPN guidelines, the MELD now also includes the serum sodium level.

The original study analysed the mortality predictors in 231 patients undergoing elective transjugular intrahepatic portosystemic shunt (TIPS) placement.

The model's validity (in predicting mortality) was tested in 4 independent data sets, via concordance (c)-statistic:

(1) patients hospitalized for hepatic decompensation (c-statistic = 0.87);

(2) ambulatory patients with noncholestatic cirrhosis (c-statistic = 0.80);

(3) patients with primary biliary cirrhosis (c-statistic = 0.87);

(4) unselected patients from the 1980s with cirrhosis (c-statistic = 0.78).

The MELD models allow a transparent and reliable stratification of liver disease which in turn helps prioritize patients who are eligible for liver transplant.

Original sources

1. Kamath PS, Wiesner RH, Malinchoc M, Kremers W, Therneau TM, Kosberg CL, D'Amico G, Dickson ER, Kim WR. A model to predict survival in patients with end-stage liver disease. Hepatology. 2001; 33(2):464-70.

2. OPTN's announcement about Sodium Inclusion

Validation

Wiesner R, Edwards E, Freeman R, Harper A, Kim R, Kamath P, Kremers W, Lake J, Howard T, Merion RM, Wolfe RA, Krom R; United Network for Organ Sharing Liver Disease Severity Score Committee. Model for end-stage liver disease (MELD) and allocation of donor livers. Gastroenterology. 2003; 124(1):91-6.

Other references

1. Kamath PS, Kim WR; Advanced Liver Disease Study Group. The model for end-stage liver disease (MELD). Hepatology. 2007; 45(3):797-805.

2. Kremers WK, van IJperen M, Kim WR, Freeman RB, Harper AM, Kamath PS, Wiesner RH. MELD score as a predictor of pretransplant and posttransplant survival in OPTN/UNOS status 1 patients. Hepatology. 2004; 39(3):764-9.

3. Biggins SW, Kim WR, Terrault NA, Saab S, Balan V, Schiano T, Benson J, Therneau T, Kremers W, Wiesner R, Kamath P, Klintmalm G. Evidence-based incorporation of serum sodium concentration into MELD. Gastroenterology. 2006; 130(6):1652-60.