Predictive Value of Blood Ammonia in the Prognosis of Acute Liver Failure Evaluated by Receiver Operating Characteristic Curves.

BACKGROUND

To investigate the predictive value of blood ammonia (BLA) quantification in the prognosis of acute liver failure (ALF).

METHODS

Seventy-one patients with ALF were enrolled and BLA concentration was measured in all patients. After following up for 28 days, patients were divided into two groups: the surviving group (n = 21) and the deceased group (n = 50). An independent-samples t-test was used to compare BLA concentrations between the two groups, and receiver operating characteristic curves were used to ¬evaluate the predictive value of BLA in the prognosis of ALF. A fourfold table analysis was performed with the determined BLA cutoff value.

RESULTS

The average concentration of BLA in the deceased group was significantly higher compared with the surviving group (144.50 µmol/L vs. 106 µmol/L, respectively; P = .035). The cutoff BLA concentration for a good ALF prognosis was 122.5 µmol/L. The area under the curve was 0.659. Both the sensitivity and specificity were >0.6. The 95% CIs for sensitivity and specificity were 0.452-0.733 and 0.477-0.878, respectively. The fourfold table analysis revealed a positive predictive value of 83.3%, a negative predictive value of 42.9%, a misdiagnosis rate of 28.6%, and an accuracy of 63.4%.

CONCLUSION

With a cutoff BLA concentration of 122.5 µmol/L, the prognosis of ALF could be predicted with high sensitivity and specificity, a positive predictive value, a low misdiagnosis rate, and good accuracy.