Background One of the unmet needs in patients with metabolic risks is the prediction of metabolic liver disease (MLD) by noninvasive tests (NITs). Objective The primary aim of this study was to construct a new quantitative test for the diagnosis of nonalcoholic steatohepatitis (NASH) using a simplified histological definition. Patients and methods As a reference, we used a simplified histological definition of NASH derived from the FLIP-CRNdefinition that does not require the presence of steatosis and the presence of both lobular inflammation and ballooning. We analyzed 1081 patients from two prospective cohorts at risk of MLD who had biopsies and contemporaneous blood samples. These patients were divided randomly into a training group (n= 541) and a control group (n= 540) for internal validation. The new test was compared with standard tests, and applied in two large populations at risk of MLD. Results Out of 1081 patients with biopsy, 39 (3.6%) cases with significant inflammatory activity or fibrosis (A2orF2) were missed by the current histological definitions. The combination of 11 parameters permitted to construct a test (NIT-NASHs) predicting NASH with an area under the receiver operating characteristic curve (AUROC) of 0.773 (95% confidence interval: 0.730–0.810), confirmed in the control group 0.814 (0.774–0.847). The AUROCs of NIT-NASHs were higher (all P<0.001) than those of ActiTest, FIB4, BARD, and nonalcoholic fatty liver disease scores. A combination of NIT-NASHs with FibroTest (AUROC=0.800; 0.759–0.835) enabled a better prediction (P< 0.0001) of significant MLD, A2orF2, than the ActiTest–FibroTest combination. Conclusion These results suggested that this new test enables a quantitative assessment of NASH, and when associated with the FibroTest, identifies cases with clinically significant MLD. An external validation is needed.