Diagnostic accuracy of exhaled nitric oxide for the non-invasive identification of patients with fibrotic metabolic dysfunction-associated steatohepatitis

Abstract

Background: Fibrotic metabolic dysfunction-associated steatohepatitis (MASH) is a condition at risk of progressing to advanced liver disease. We examined whether an innovative exhaled nitric oxide (eNO) breath test (BT) can accurately diagnose fibrotic MASH without requiring blood tests.

Methods: One hundred and forty-seven patients with MASH were recruited, and all tests were undertaken within 1 week of recruitment. With fibrotic MASH (NAS ≥ 4 and fibrosis stage ≥ 2) as the main outcome indicator, the diagnostic efficacy of eNO in identifying fibrotic MASH was compared to other validated models for advanced fibrosis requiring venesection, namely FAST, Agile 3⁺, and FIB-4 scores.

Results: The mean age was 40.36 ± 12.28 years, 73.5% were men. Mean body mass index was 28.83 ± 4.31 kg/m². The proportion of fibrotic MASH was 29.25%. The area under the receiver operating curve for eNO in diagnosing fibrotic MASH was 0.737 [95% CI 0.650-0.823], which was comparable to FAST (0.751 [0.656-0.846]), Agile 3⁺ (0.764 [0.670-0.858]), and FIB-4 (0.721 [0.620-0.821]) (all DeLong test p > 0.05). A cut-off of eNO <8.5 ppb gave a sensitivity of 86.0% and a negative predictive value of 88.5% for ruling-out fibrotic MASH. A cut-off of eNO >13.5 ppb provided a specificity of 91.3% and a positive predictive value of 65.4% for ruling-in fibrotic MASH. Sensitivity analyses demonstrated that the diagnostic efficacy of eNO was similar across characteristics such as age. Moreover, adding vibration-controlled transient elastography-LSM (liver stiffness measurement) reduced the uncertainty interval from 46.9% to 39.5%.

Conclusions: The eNO-BT is a promising simple test for non-invasively identifying fibrotic MASH, and its performance is further improved by adding LSM measurement.

Keywords: Exhaled nitric oxide; breath test; fibrotic MASH.

Figure 1.

Diagnostic performance of eNO concentration. (A) AUROC of eNO concentration for the non-invasive identification of fibrotic MASH. (B) Sensitivity, specificity, PPV, and NPV versus all possible eNO concentrations. AUROC: area under receiver operation characteristics; PPV: positive predictive value; NPV: negative predictive value.

Figure 2.

Stratification with a rule-out, “grey zone,” and rule-in zone when applying eNO to identify fibrotic MASH. (A) Using cut-off values of eNO. (B) Using cut-off values of eNO and LSM. LSM: liver stiffness measurement.

Figure 3.

Subjects ruled out and ruled in or remaining in the “grey zone” after: (A) applying the currently recommended FAST cut-offs (0.35, 0.67) or (B) applying the eNO cut-offs (8.5 ppb, 13.5 ppb) obtained herein or (C) applying both the LSM cut-off (9.7 kPa) and eNO cut-offs (8.5 ppb, 13.5 ppb). One full human figure represents 2% of all subjects. Arrows indicate the number (and %) of reclassified patients. For example, when applying LSM as an aid, 10 fibrotic MASH patients (6.8% of the overall patient population) in the “grey zone” were ruled in with their correct diagnosis.