S index: a predictor comparable to ultrasound shear wave elastography in assessing liver fibrosis in patients with chronic hepatitis B.

Background: Chronic hepatitis B poses a major global health challenge, especially in developing countries. It significantly contributes to morbidity and mortality from liver cirrhosis and hepatocellular carcinoma.

Objective: To evaluate diagnostic performance of ultrasound shear wave elastography (USWE), S index, Z index, Fibrometer in continuous differentiation of liver fibrosis in a retrospective chronic hepatitis B patients' cohort.

Materials And Methods: We collected liver stiffness values measured by USWE and laboratory indicators from 146 patients with chronic hepatitis B at Baoji Central Hospital. Serum fibrosis models were calculated using formulas, including S index, Z index, and Fibrometer. Using liver biopsy pathology as a reference, the diagnostic efficacy of each indicator for liver fibrosis staging was evaluated using receiver operating characteristic curves (ROC).

Results: S index and USWE demonstrated comparable diagnostic accuracy for liver fibrosis staging with areas under ROC (AUCs) of 0.791 vs. 0.860 (p = 0.679) for significant fibrosis (S ≥ 2), 0.867 vs. 0.942 (p = 0.074) for severe fibrosis (S ≥ 3), and 0.961 vs. 0.932 (p = 0.508) for cirrhosis (S4). The two indices exhibited superior performance over Fibrometer across all stages (S index/USWE vs. Fibrometer-AUCs: 0.791/0.806 vs. 0.575, < 0.001 for S ≥ 2; 0.867/0.940 vs. 0.625, p < 0.001 for S ≥ 3; 0.961/0.932 vs. 0.781, p = 0.004/0.025 for S4). Compared with Z index, they showed better diagnostic capacity for S ≥ 2 (AUCs 0.791/0.806 vs. 0.575, p < 0.001) and S ≥ 3 (0.867/0.942 vs. 0.673, p < 0.001), while maintaining equivalent accuracy for cirrhosis detection (AUCs 0.961/0.932 vs. 0.914, p = 0.209/0.747).

Conclusion: The S index is equally effective as the USWE in diagnosing liver fibrosis among patients with chronic hepatitis B, and it is superior to both the Z index and Fibrometer.