In the majority of patients, NAFLD is commonly associated with metabolic comorbidities such as obesity, diabetes mellitus, and dyslipidemia. Features of metabolic syndrome are not only highly prevalent in patients with NAFLD, but components of the syndrome also increase the risk of developing NAFLD. This was found by Chalasani and his coworkers in their study and runs with our results [11,12,13,14].
Obesity (excessive body mass index [BMI] and visceral obesity) is the most common and well-documented risk factor for NAFLD. Sasaki and his colleagues and Subichin with his coworkers found in their study that the majority (> 95%) of patients with severe obesity undergoing bariatric surgery had NAFLD which was in agreement with our results where there was a good correlation between the occurrence of fatty liver and increased body weight and BMI of patients [15, 16].
Wu and his colleagues found that high serum triglyceride (TG) levels and low serum high-density lipoprotein (HDL) levels are also common in patients with NAFLD and the prevalence of NAFLD in individuals with dyslipidemia attending lipid clinics have been estimated to be 50% [17]. In agreement with that, our results revealed a good correlation between NAFLD and the increase in serum cholesterol, LDL, and TG in patients than in controls.
In a large, cross-sectional study conducted by Chalasani and his coworkers among 44,767 Taiwanese patients who attended a single clinic, the enrollees were stratified into four subgroups based on their total cholesterol to HDL cholesterol and TG to HDL cholesterol ratios. The overall prevalence rate of NAFLD was 53.76%; however, the NAFLD prevalence rate for those with the lowest total cholesterol to HDL-cholesterol and TG to HDL cholesterol ratios was 33.41%, whereas the prevalence rate in the group with the highest ratios was 78.04% [14].
Liver enzyme levels have low sensitivity and specificity and do not predict clinical outcomes and although elevated liver enzyme levels (i.e., AST and ALT levels) occur more commonly in patients with NASH compared with simple hepatic steatosis, not all patients with NASH have elevated AST or ALT levels. Even though a persistently elevated level of ALT can be associated with an increased risk of NAFLD progression, patients with advanced disease often have normal liver enzyme levels, making the identification of at-risk patients more conflicting [18]. In disagreement with that, our results documented that there was a significant increase in liver enzymes (AST, ALT) and total serum bilirubin in patients with fatty liver with a significant decrease in total serum albumin without significant change in INR between patients and controls.
Our results revealed that there was a positive correlation between NAFLD and the advanced stages in FIB-4 score. Angulo and his colleagues studied the histology of NAFLD patients and found that the most important histological feature of NAFLD associated with long-term mortality is fibrosis; specifically, zone 3 sinusoidal fibrosis plus periportal fibrosis (stage 2) to advanced (bridging) fibrosis [stage 3] or cirrhosis [stage 4], which was in agreement with our results [19].
Nobili et al. showed that liver stiffness (LS) detected by TE at more than 9 kPa was associated with a high stage of fibrosis in pathology. Yoneda et al. evaluated LS in 97 NAFLD patients and observed that there was a significant correlation between METAVIR score and TE through different stages. He also concluded that using TE in detecting the level of fibrosis in NAFLD cases has high accuracy and can be a good alternative for liver biopsy in patients who cannot undergo invasive procedures, which adds to our results [20].
Cassinotto et al. demonstrated that TE can successfully identify significant fibrosis in the majority of patients. Fortunately, fibrosis is the histopathological feature most predictive of poor outcomes in NAFLD. It is also known that NAFLD patients who develop NASH are at substantially increased risk for progression of liver disease, with fibrosis progression rates that have been estimated to be one stage every 7 years, significantly higher than patients with non-NASH NAFLD. Thus, it is important to identify which patients had NASH from those with non-NASH NAFLD and to assess whether any elastography-based imaging modality can accurately discriminate those patients liable to develop NASH (based on significant fibrosis detected by TE) from those with non-NASH NAFLD which adds value to our results [21].
Patel and Sebastiani studied the various laboratory-based and radiation-based non-invasive tests (NITs) for the assessment of liver fibrosis and concluded that vibration-controlled transient elastography (VCTE) was a rapid, safe, and reproducible procedure for liver stiffness measurement (LSM) assessment that can be performed at the bedside with immediate results, and it represents a true point-of-care assessment and is the most widely used and validated technique for non-invasive imaging assessment of liver fibrosis. They also concluded that understanding the strengths and limitations of NITs would allow for more judicious interpretation in the clinical context, where NITs should be viewed as complementary to, rather than as a replacement for, liver biopsy [22].
In a recent study, Goyale et al. studied 105 adult patients with varying severity of NAFLD in a prospective, cross-sectional study. They concluded from their work that FibroScan was an accurate and accepted non-invasive tool that has shown concordance with liver biopsy results. In practice, NAFLD disease severity is usually assessed by a combination of the non-invasive clinical, biochemical, and sonographic parameters, with liver biopsy being reserved for patients with suspected progressive or advanced disease [23].
Eddowes et al. estimated the accuracy of Fibroscan vibration-controlled transient elastography liver stiffness measurement (LSMs) in assessing fibrosis in patients with suspected NAFLD in comparison with the standard-of-care liver biopsy. They found that LSM assessment achieved an area under the receiver operating characteristic curves (AUROC) values ranging from 0.80 to 0.89 for F3 and F4 cases. They concluded that LSMs by FibroScan are accurate non-invasive methods for assessing liver steatosis and fibrosis in patients with NAFLD [24]. In the current work, LSMs by FibroScan showed a good correlation with each FIB-4 score and NAFLD fibrosis score with AUROC of 0.81–1.0 and 0.59–0.88, respectively, in advanced cases ≥ F3.