Navigating NAFLD: Unveiling the approach to mitigate the impact of NAFLD
In the assessment of disease progression, prior data have shown that the presence of NASH and increasing stages of liver fibrosis are important predictors of disease progression. Fibrosis is a component of NASH, while NASH is thought to be a prerequisite for fibrosis. In a prospective, multicenter follow-up study of NAFLD evaluated by liver biopsies (n = 1,773), over a median follow-up of 4 years, 37 (2%) developed hepatic decompensation, while 47 (3%) died from any cause, which included ESLD (n = 12), cardiovascular complications (n = 4), and malignancies (n = 12), including HCC (n = 9).9 It is not entirely surprising that advanced fibrosis and cirrhosis was highly associated with the development of hepatic decompensation. In their multivariable analysis, patients with F3-4 had a 13.8-fold (95% confidence interval [CI]: 4.6, 41.0) increase in the hazard of reaching a MELD score of 15 compared to those with F0-2. In addition, all-cause mortality was 17.2-fold (95% CI: 5.2, 56.6) higher with F3-4 compared to F0-2.
These data have been borne out by a larger body of literature on the topic. In a recent meta-analysis assessing the relation between liver fibrosis and future mortality, which included 17,301 subjects with NAFLD, patients with at least stage 2 fibrosis experience a significantly increased risk of liver-related and overall mortality, a trend that accelerates at higher fibrosis stages.10 These point to liver fibrosis as the singular determinant of long-term prognosis, in comparison, for example, with the diagnosis of NASH. Hagström conducted a retrospective cohort study of patients with biopsy-proven NAFLD in Sweden. When fibrosis stage and histological diagnosis of NASH were considered together, NASH did not have an impact on overall mortality (hazard ratio [HR] = 0.83, P = .29) or liver morbidity (HR = 0.62, P = .25).11
On an individual level, factors that affect fibrosis progression are not as well studied. It is commonly believed that demographic factors (e.g., age, sex and race), genetic polymorphisms (e.g., PNPLA3, TM6SF2), clinical comorbidities (e.g., obesity, DM, and sleep apnea), and environmental factors (e.g., smoking) may accelerate fibrosis and disease outcomes, although prospective data are sparse to estimate the extent these individual variables affect progression.12 Recent guidelines remain silent about whether and how these data may be incorporated in screening for NAFLD in the population.
Assessment of liver fibrosis
The traditional means to detect liver fibrosis is liver histology, which also assesses steatosis, individual components of NASH and, often importantly, other concomitant liver pathology. In reality, however, liver biopsies have several limitations including the risk of complications, patient discomfort, economic costs, and sampling variability. Increasingly, “noninvasive” methods have been used to estimate liver fibrosis in patients with NAFLD. Liver elastography estimates the physical stiffness of the organ, which may be measured by MRI or ultrasound. Among ultrasound-based technologies, vibration-controlled transient elastography (VCTE) is more widely accepted and affordable although it may not be as accurate as MR elastography.13
