Development and validation of nonalcoholic fatty liver disease test: a simple sensitive and specific marker for early diagnosis of nonalcoholic fatty liver disease

Aim This study aimed to develop a noninvasive test for identifying patients with nonalcoholic fatty liver disease (NAFLD) based on clinical and routine laboratory data. Methods The developed model 'NAFLD test' was compared to the most commonly used NAFLD scores and then validated in three groups of NAFLD patients from five centers in Egypt, China, and Chile. Patients were divided into the discovery cohort (n = 212) and the validation study (n = 859). The ROC curve and stepwise multivariate discriminant analysis were used to develop and validate the NAFLD test and evaluate its diagnostic performance, which was then compared to other NAFLD scores. Results Elevated C-reactive protein (CRP), cholesterol, BMI, and alanine aminotransferase (ALT) levels were significantly associated with NAFLD (P < 0.0001). NAFLD test is depicted as (-0.695 + 0.031 × BMI + 0.003 × cholesterol + 0.014 × ALT + 0.025 × CRP) to discriminate patients with NAFLD from healthy individuals. The area under the ROC curve (AUC) of the NAFLD test was 0.92 [95% confidence interval (CI): 0.88-0.96]. The NAFLD test was the most accurate diagnostic indicator of NAFLD when compared to widely used NAFLD indices. Upon validating the NAFLD test, its AUC (95% CI) for distinguishing patients with NAFLD from healthy individuals was 0.95 (0.94-0.97), 0.90 (0.87-0.93), and 0.94 (0.91-0.97) in Egyptian, Chinese, and Chilean patients with NAFLD respectively. Conclusion The NAFLD test is a new validated diagnostic biomarker that can be utilized for the early diagnosis of NAFLD with high diagnostic performance.