NAFLD / MASLD Commonly Missed Diagnoses: What Gets Overlooked and Why

Why MASLD Is So Frequently Missed

Metabolic-associated steatotic liver disease does not hurt. Patients feel nothing in early stages, and their liver enzymes may be entirely normal. A 2023 international consensus paper in Hepatology estimated that fewer than 5 percent of people with MASLD carry a documented diagnosis, meaning the vast majority are walking around with unrecognized liver disease [1].

The diagnostic gap exists for three overlapping reasons: clinicians anchor on other explanations for elevated transaminases, the old NAFLD label caused confusion about what "non-alcoholic" actually meant, and patients with normal ALT are rarely investigated at all.

The Normal-ALT Problem

ALT can be normal in histologically confirmed MASLD, including in patients with significant fibrosis. A study of 458 biopsy-confirmed NAFLD patients found that 25 percent had ALT values within the standard reference range despite advanced histological disease [2]. Standard lab panels therefore miss a meaningful fraction of cases.

The Symptom Absence Problem

Most patients report no symptoms until decompensated cirrhosis appears. By that point, the opportunity for early intervention with lifestyle modification, GLP-1 receptor agonists, or resmetirom has passed. The American Association for the Study of Liver Diseases (AASLD) 2023 guidance states: "Clinicians should proactively screen at-risk patients rather than waiting for symptomatic presentation" [3].

The Rename Confusion Problem

The shift from NAFLD to MASLD in 2023 introduced short-term ICD coding confusion. Some electronic health records still carry both codes, and clinicians may be uncertain which applies. The new MASLD definition requires at least one cardiometabolic risk factor (overweight/obesity, type 2 diabetes, hypertension, dyslipidemia, or metabolic syndrome) alongside hepatic steatosis, replacing the older exclusion-based approach [1].

Conditions That Mimic MASLD and Get Diagnosed Instead

Several diseases produce elevated liver enzymes or hepatic steatosis on imaging and can be labeled as MASLD when they are not, or vice versa.

Alcohol-Associated Liver Disease

This is the single most common mimicker. Alcohol-associated liver disease (ALD) and MASLD share virtually identical histologic findings on biopsy, including steatosis, lobular inflammation, and hepatocyte ballooning. The only reliable separator is alcohol intake history, which patients frequently under-report.

The MASLD alcohol threshold is below 30 g/day in men and below 20 g/day in women. One standard U.S. Drink contains approximately 14 g of pure ethanol, meaning MASLD requires fewer than roughly two drinks per day for men. Phosphatidylethanol (PEth) blood testing, which detects alcohol use over the prior three to four weeks with sensitivity exceeding 90 percent, is an underused objective tool [4].

Drug-Induced Liver Injury

Drug-induced liver injury (DILI) accounts for approximately 10 percent of cases initially labeled as NAFLD in tertiary hepatology referral centers [5]. Methotrexate, amiodarone, tamoxifen, corticosteroids, and valproate all cause steatohepatitis that looks like MASLD on biopsy. A medication review is mandatory before MASLD is confirmed.

The NIH LiverTox database (livertox.nih.gov) catalogs over 1,000 agents with hepatotoxic potential and should be consulted in any patient with steatohepatitis and significant polypharmacy.

Thyroid Disease

Hypothyroidism causes hepatic steatosis through decreased fatty acid oxidation and reduced lipoprotein clearance. A meta-analysis of 13 studies (N=35,082) found that subclinical hypothyroidism was associated with a 1.27-fold higher odds of NAFLD (OR 1.27, 95% CI 1.10 to 1.47) [6]. TSH is not included in standard liver workup panels, and hypothyroidism is missed as a contributory or primary driver more often than it should be.

Celiac Disease

Celiac disease produces transaminase elevation in up to 40 percent of untreated patients, and hepatic steatosis occurs in a subset. Because celiac disease is itself underdiagnosed (estimated 1 in 133 Americans, with only 17 percent having a formal diagnosis), it can lurk beneath an apparent MASLD label [7]. Tissue transglutaminase IgA (tTG-IgA) testing costs under $30 and is not part of routine liver workup.

Wilson's Disease

Wilson's disease is rare but dangerous to miss. It affects roughly 1 in 30,000 people and causes hepatic copper accumulation that produces steatohepatitis indistinguishable from MASLD. The AASLD recommends serum ceruloplasmin screening in all patients under age 40 with unexplained liver disease [3]. Missed Wilson's disease leads to cirrhosis and neuropsychiatric deterioration that is preventable with chelation therapy.

Autoimmune Hepatitis

Autoimmune hepatitis (AIH) can present indolently with mild ALT elevation, and imaging may show steatosis if the patient also has metabolic risk factors. Up to 15 percent of AIH cases are initially labeled as NAFLD before autoimmune markers are checked. ANA, anti-smooth muscle antibody (ASMA), and serum immunoglobulin G should be part of any systematic liver workup [3].

Co-Diagnoses Routinely Missed in Confirmed MASLD Patients

The diagnostic failure runs in both directions. When MASLD is correctly identified, clinicians often stop there and fail to document the metabolic conditions that almost always coexist.

Type 2 Diabetes and Prediabetes

Type 2 diabetes is present in approximately 22 percent of MASLD patients worldwide, and prediabetes affects an additional 30 to 40 percent [8]. The ADA 2024 Standards of Care state: "Adults with MASLD should be evaluated for type 2 diabetes with fasting glucose and HbA1c" [9]. Despite this, glycemic screening is frequently omitted at the time of liver disease diagnosis.

This matters because uncontrolled diabetes accelerates fibrosis progression. The rate of fibrosis progression in MASLD patients with concurrent type 2 diabetes is approximately twice that of metabolically healthier counterparts [8].

Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is present in 30 to 40 percent of MASLD patients but is confirmed in fewer than half of those affected because polysomnography is rarely ordered during liver workup [10]. Intermittent hypoxia from OSA independently worsens hepatic steatosis and inflammation through oxidative stress pathways. An Epworth Sleepiness Scale score of 10 or higher should prompt sleep medicine referral.

Cardiovascular Risk

Cardiovascular disease, not cirrhosis, is the leading cause of death in MASLD patients. A landmark 2011 meta-analysis of 34 studies found that NAFLD was associated with a 1.64-fold increased risk of fatal and non-fatal cardiovascular events (OR 1.64, 95% CI 1.26 to 2.13) [11]. Yet lipid panels, blood pressure control, and 10-year ASCVD risk calculations are inconsistently documented in MASLD clinic notes.

The HealthRX clinical review team uses a structured co-diagnosis checklist for every confirmed MASLD patient: HbA1c, fasting lipids, blood pressure classification, Epworth score, TSH, tTG-IgA if BMI <25, and 10-year ASCVD risk via the Pooled Cohort Equations. This framework reduces the odds that a concurrent diagnosable condition goes unaddressed at the first clinical encounter.

How to Correctly Work Up Suspected MASLD

Step 1: Confirm Steatosis

Ultrasound is the standard first-line imaging test. It detects steatosis when hepatic fat exceeds roughly 20 to 30 percent of liver volume, with sensitivity of 60 to 94 percent depending on operator experience and patient body habitus. Controlled attenuation parameter (CAP) via FibroScan gives a more quantitative fat measurement and is reproducible across serial visits [12].

MRI-proton density fat fraction (MRI-PDFF) is the most accurate non-invasive steatosis quantifier, with an area under the curve exceeding 0.90 for detecting 5 percent or more hepatic fat. It is used in clinical trials but is not yet standard of care for routine diagnosis [12].

Step 2: Stage Fibrosis Without Biopsy

The FIB-4 index, calculated as (age x AST) / (platelet count x ALT square root), is recommended by AASLD, EASL, and AACE as the first-line fibrosis assessment tool [3]. A FIB-4 score below 1.30 has a negative predictive value exceeding 90 percent for advanced fibrosis. A score above 2.67 warrants further evaluation with liver stiffness measurement.

FibroScan liver stiffness measurement (LSM) above 8.0 kPa correlates with F2 or higher fibrosis and above 12.0 kPa suggests cirrhosis. Adding Enhanced Liver Fibrosis (ELF) score or Pro-C3 improves specificity in indeterminate FIB-4 ranges (1.30 to 2.67) [13].

Step 3: Exclude Alternative Diagnoses

Before MASLD is confirmed, the following minimum workup should be completed: alcohol intake history supplemented with PEth if under-reporting is suspected, medication review against the NIH LiverTox database, hepatitis B surface antigen and hepatitis C antibody, TSH, ANA and ASMA, serum immunoglobulin G, ceruloplasmin if age <40, and tTG-IgA with total IgA to exclude celiac disease [3].

Hereditary hemochromatosis should also be excluded with transferrin saturation and ferritin; a saturation above 45 percent warrants HFE gene testing.

Step 4: Assess Cardiometabolic Risk

Document the presence or absence of each MASLD cardiometabolic criterion: BMI or waist circumference, fasting glucose and HbA1c, triglycerides, HDL cholesterol, and blood pressure. Calculate the 10-year ASCVD risk. These data points determine both MASLD diagnosis confirmation and guide treatment prioritization.

Current Treatment Options and Where Misdiagnosis Delays Them

Resmetirom (Rezdiffra)

Resmetirom received FDA approval in March 2024 as the first disease-specific pharmacotherapy for MASH (metabolic-associated steatohepatitis) with fibrosis stages F2 to F3 [14]. The MAESTRO-NASH trial (N=966) showed that resmetirom 100 mg daily achieved NASH resolution without worsening fibrosis in 29.9 percent of patients versus 9.7 percent with placebo (P<0.001) [15]. Patients who are misdiagnosed or never staged cannot access this therapy.

The approved indication requires documented MASH with at least F2 fibrosis on biopsy or non-invasive equivalent. Clinicians who skip fibrosis staging leave eligible patients without an approved treatment option.

GLP-1 Receptor Agonists

Semaglutide 0.4 mg daily (subcutaneous, a dose used in the phase 2 NASH trial) reduced histological NASH resolution to 59 percent versus 17 percent with placebo, though fibrosis improvement did not reach statistical significance in that trial (N=320) [16]. The larger ESSENCE trial is ongoing and expected to report fibrosis outcomes in 2025.

Tirzepatide, a dual GIP/GLP-1 agonist, reduced MRI-PDFF hepatic fat by 54.5 percent from baseline at 52 weeks in the SURMOUNT-1 substudy compared with 7.5 percent for placebo [17]. Phase 3 MASH-specific trials are underway.

These agents are often prescribed for weight loss or glycemic control without the prescriber documenting MASLD improvement as a secondary goal, which means the hepatic benefit is never tracked or attributed.

Lifestyle Modification

A 7 to 10 percent reduction in body weight produces histological NASH resolution in approximately 50 percent of patients. Weight loss of 10 percent or more is associated with fibrosis regression in up to 45 percent of patients [18]. Misdiagnosis or no diagnosis means no structured weight-loss counseling is initiated, and the window for lifestyle-driven regression closes as fibrosis advances.

Special Populations Where MASLD Is Most Frequently Missed

Lean MASLD

MASLD affects patients with BMI <25 (lean MASLD) in roughly 5 to 7 percent of cases globally. These patients are rarely screened because the clinical assumption is that fatty liver disease requires obesity. Lean MASLD carries a disproportionately high cardiovascular risk relative to its low body weight and may have a distinct genetic driver, including PNPLA3 and TM6SF2 variants [19]. A normal BMI does not exclude MASLD.

Women With Polycystic Ovary Syndrome

PCOS affects 6 to 12 percent of reproductive-age women, and MASLD is present in up to 55 percent of women with PCOS, independent of BMI. Insulin resistance, not obesity per se, drives the hepatic fat accumulation in this group [20]. Gynecologists managing PCOS rarely order liver imaging, and hepatologists rarely ask about PCOS history. The connection between the two conditions is systematically under-documented.

Pediatric Patients

MASLD is the most common chronic liver disease in children, affecting approximately 10 percent of the pediatric population and up to 40 percent of obese children. Pediatric MASLD is routinely attributed to "normal childhood weight gain" and goes uninvestigated. ALT thresholds differ by sex and age in children; using adult reference ranges further masks abnormal results [21].

What the Guidelines Say Clinicians Should Do

The AASLD 2023 Practice Guidance, the EASL 2024 Clinical Practice Guidelines, and the AACE 2022 Consensus Statement all converge on a common approach. Screen patients with type 2 diabetes, obesity, or metabolic syndrome for MASLD using ALT and liver ultrasound. Use FIB-4 to risk-stratify. Refer patients with FIB-4 above 1.30 or LSM above 8.0 kPa to hepatology.

The AASLD explicitly states: "A FIB-4 <1.30 in patients <65 years can reliably exclude advanced fibrosis without additional testing in most cases, while a FIB-4 >2.67 should prompt liver stiffness measurement" [3].

Despite these recommendations, a 2022 survey of 1,200 primary care physicians found that fewer than 30 percent routinely calculated FIB-4 in patients with metabolic risk factors and elevated transaminases. Most relied on gastroenterology referral thresholds that were not evidence-based [22].