Editorial: progress towards a simple tool for screening for hepatic steatosis in the general population

Non-alcoholic fatty liver disease (NAFLD) is a significant cause of endstage liver disease and hepatocellular carcinoma. Despite, studies showing that 20%-40% of the general population have hepatic steatosis, it often goes unrecognised in primary care. Current guidelines do not advocate population screening for NAFLD, largely due to the lack of a simple, cost-effective test for steatosis, and the fact there are relatively few treatment options available. However, several drugs for NAFLD are in advanced clinical trials and it is likely that some will be licensed soon. Therefore, development of a simple test to identify subjects with steatosis in the population would be advantageous. AP&T recently published an interesting study describing the development of a model to predict steatosis using routine clinical and laboratory parameters. The study included 922 individuals, selected randomly from the general population of Hong Kong, who had a comprehensive assessment for NAFLD, including MR spectroscopy. Using advanced statistical modelling techniques four models were developed to predict the presence of steatosis (>5%), which all had good diagnostic precision (area under receiver operator curve [AUROC] 0.87-0.9). The authors concluded that the “NAFLD ridge score” offered the best balance between efficacy and simplicity. This model included 6 parameters (serum triglycerides, alanine aminotransferase, high density lipoprotein cholesterol, haemoglobin A1c, white cell count and the presence of hypertension) that are routinely available for individuals undergoing medical checkups. The AUROCs to predict steatosis for this score were 0.87 and 0.88 in the training and validation cohorts respectively. Using the lower cut-off (0.24) the negative predictive value for steatosis was 96%, suggesting the score is reliable in excluding steatosis. Using the upper cut-off (0.44) the positive predictive value for steatosis was 70%. Therefore, the main value of this score would be to exclude steatosis, similar to the use of available simple non-invasive fibrosis scores. The NAFLD ridge score has advantages over current scores to predict steatosis (e.g. fatty liver index) as it does not require input of anthropometric measures, which are not always available. Given its simplicity the NAFLD ridge score could be used to screen individuals periodically to identify/exclude NAFLD. Although the study was well conducted, it has few limitations that are worthy of discussion. Firstly, this study was conducted in a Chinese population so the findings need to be confirmed in other ethnicities. Secondly, the impact of alcohol consumption on the performance of the score requires further study. In addition, the effect of treatment of diabetes and dyslipidaemia on the performance of the score was not addressed. In our view, the NAFLD ridge score may also benefit from a single cut-off with optimum sensitivity and specificity to predict steatosis. While this would reduce its overall accuracy, practically it would simplify use of the tool and eliminate the indeterminate cases. It would be interesting to see the NAFLD ridge score combined with a simple non-invasive fibrosis test (e.g FIB-4 score), as a combination of scores may be more efficient in identifying those individuals with NAFLD most in need of treatment.