Clinical profiles and mortality rates are similar for metabolic dysfunction-associated steatotic liver disease and non-alcoholic fatty liver disease.

Background & Aims: Recently, the term metabolic dysfunction-associated steatotic liver disease (MASLD) has replaced non-alcoholic fatty liver disease (NAFLD). Concern remains regarding whether the evidence generated under the NAFLD definition can be used for MASLD. We compared the clinical profile and outcomes of NAFLD to MASLD using tertiary care- and population-based data.

Methods: Comparison data were obtained from our NAFLD database and the National Health and Nutrition Examination Survey (NHANES III). Clinical profiles and non-invasive tests (enhanced liver fibrosis [ELF] score, fibrosis-4 index [FIB-4] and vibration-controlled transient elastography) were compared. Mortality data were obtained from NHANES-National Death Index. All-cause mortality was assessed by Cox proportional hazards regression models and cause-specific mortality by competing risk analysis.

Results: There were 6,429 patients in the NAFLD database (age: 54 ± 12 years, 42% male, BMI 35.4 ± 8.3, waist circumference 112 ± 17 cm, 52% type 2 diabetes). Average scores for ELF, FIB-4 and liver stiffness were 9.6 ± 1.2, 1.69 ± 1.24,14.0 ± 11.8 kPa, respectively; 99% met MASLD criteria; 95% met MASLD on BMI only. Predictive accuracy of ELF and FIB-4 were identical between MASLD and NAFLD. We included 12,519 eligible participants from NHANES (age 43.00 years, 47.38% male, 22.70% obese, 7.28% type 2 diabetes, 82.51% ≥1 cardiometabolic criteria). Among the NHANES study population, there was excellent concordance between MASLD and NAFLD diagnoses: Cohen's kappa coefficient: 0.968 (95% CI 0.962-0.973) with 5.29% of NAFLD cases not meeting MASLD criteria. After a median follow-up of 22.83 years, there were no mortality differences between MASLD and NAFLD diagnoses (p values ≥0.05).

Conclusions: NAFLD and MASLD are similar except individuals with MASLD seem to be older with slightly higher mortality risk, likely owing to cardiometabolic risk factors. Clinical profiles and non-invasive test thresholds were also identical. These data provide evidence that NAFLD and MASLD terminologies can be used interchangeably. For the small proportion of patients with NAFLD who do not meet MASLD criteria, further consideration is needed.

Impact And Implications: In June 2023, new terminology (MASLD) was adopted to replace the term NAFLD as a means to better describe what the liver disease is rather than what it is not, as well as to potentially reduce stigma. Given that MASLD requires at least one cardiometabolic risk factor, questions were raised as to whether this change in the definition would nullify the similarities between NAFLD and MASLD and require new evidence to be generated for MASLD. We used our NAFLD database and a US population-based database to show that the vast majority of patients with NAFLD fulfill criteria for MASLD. Non-invasive tests performed similarly in both groups. Mortality risk was slightly higher in those with MASLD, which is attributed to the presence of cardiometabolic risks. These results provide evidence that data generated in the past three decades for NAFLD can be used interchangeably for MASLD.