Breath-Ammonia Testing of Healthy Subjects and Patients with Cirrhosis

Abstract

Hepatic encephalopathy (HE) is a serious neuropsychiatric complication in both acute and chronic liver disease. To establish the utility of a portable noninvasive method to measure ammonia in the breath of healthy subjects and patients with HE. The study included 106 subjects: 44 women and 62 men, 51 healthy and 55 cirrhotic. The breath ammonia was measured with an electrochemical sensor and expressed in parts/billion (ppb). The breath ammonia in healthy subjects had an average value of 151.4 ppb (95% confidence interval [CI]: 149.4-153.4) and the average value in cirrhotic patients was 169.9 ppb (95% CI: 163.5-176.2) (P < 0.0001). In cirrhotic patients with and without HE, the corresponding values were 184.1 ppb (95% CI: 167.7-200.6) and 162.9 ppb (95% CI: 158.8-167.0), respectively (P = 0.0011). Ammonia levels ≥ 165 ppb permitted a differentiation between healthy and cirrhotic subjects; the area under the receiver operating characteristic (ROC) curve for the ammonia-level values in cirrhotic versus control patients was 0.86 (95% CI: 0.79-0.93). In cirrhotic patients, ammonia levels ≥ 175 ppb permitted the distinction between patients with and without HE; the area under the ROC curve in cirrhotic patients with versus without HE was 0.83 (95% CI: 0.73-0.94). A portable sensor for measuring breath ammonia can be developed. If the results of the present study are confirmed, breath-ammonia determinations could produce a significant impact on the care of patients with cirrhosis and could even include the possibility of self-monitoring.