FibroScan-AST (FAST) Score for Nonalcoholic Steatohepatitis – Validation in an Indian Cohort

The FibroScan-AST (FAST) score was recently described to detect patients with nonalcoholic steatohepatitis (NASH) having elevated nonalcoholic fatty liver disease (NAFLD) activity score (NAS ≥ 4) and significant fibrosis (≥ F2) on liver biopsy (NASH+ NAS ≥ 4 + F ≥ 2). The aim of this study was to validate the FAST score in Indian patients with NAFLD and to derive optimal cut-offs. Sixty patients with biopsy-proven NAFLD [men: 38 (63.3%), age 40 (32–52) years] with all parameters for assessing the FAST score within 3 months of liver histology were retrospectively analysed. Histological NASH was present in 17 patients (28.3%), while 11 (18.3%) patients had NASH + NAS ≥ 4 + F ≥ 2. The area under the curve (AUROC) of the FAST score for discriminating NASH + NAS ≥ 4 + F ≥ 2 was 0.81. Using cut-offs by Newsome et al, the rule-out cut-off (FAST: ≤ 0.35) had a negative predictive value (NPV) of 0.88 [sensitivity: 0.91, specificity: 0.14, negative likelihood ratio (LR): 0.64], while the rule-in cut-off (FAST: ≥ 0.67) had a positive predictive value (PPV) of 0.33 (sensitivity: 0.73, specificity: 0.67, positive LR: 2.22). Fifteen (25%) patients were correctly classified as per histology, while 28 (46.67%) patients fell in the grey zone. On recalculating the optimal cut-offs for our patients, the rule-out cut-off (FAST: ≤ 0.55) had an NPV of 0.95 (sensitivity: 0.90, specificity: 0.45, negative LR: 0.21), while the optimal rule-in cut-off (FAST: ≥ 0.78) had a PPV of 0.70 (sensitivity: 0.64, specificity 0.94, positive LR: 10.39). With these cut-offs, 27 (45%) patients fell in the grey zone and 29 (48.3%) were correctly classified as per histology, performing better than the cut-offs by Newsome et al ( P < 0.001). The FAST score demonstrates good AUROC for detecting NASH with significant fibrosis and inflammation on histology. Cut-offs should be recalibrated based on prevalence of disease. India has a high burden of NAFLD with an estimated 25 million patients at potential risk for significant liver disease. Liver biopsy remains the gold standard for diagnosing NASH, although its application in routine clinical practice is limited. Noninvasive tests for the simultaneous detection of steatosis, inflammation and fibrosis are thus the need of the hour. The FAST score has been recently suggested for the noninvasive detection of NASH with significant fibrosis (≥ F2) and inflammation (NAS ≥ 4) on liver biopsy. We validated the utility of the FAST score for detecting NASH with significant fibrosis and inflammation on liver biopsy in Indian patients with NAFLD. This noninvasive, easy-to-use and nonproprietary FAST score can correctly classify disease severity in more than 50% patients. However, our results suggest that cut-offs should be recalibrated based on the anticipated prevalence of NASH + NAS ≥ 4 + F ≥ 2 in the given population.