Diagnostic Accuracy of CT for the Detection of Hepatic Steatosis: A Systematic Review and Meta-Analysis

Academic Background

Hepatic steatosis is the result of the abnormal accumulation of triglycerides in hepatocytes, which can initiate a cascade of inflammatory responses, referred to as steatotic liver disease (SLD). Metabolic dysfunction–associated SLD is the most common form of SLD in the United States and worldwide and is rapidly becoming the most common cause of chronic liver disease. Hepatic steatosis is a significant risk factor for cardiovascular disease, fibrosis, cirrhosis, liver cancer, liver failure, and death. Early detection of this condition is critical to allow early intervention and prevent complications.

Traditionally, liver biopsy has been the reference standard for the diagnosis and grading of hepatic steatosis. More recently, MRI-based fat quantification techniques have been introduced as alternatives to biopsy, specifically the MRI proton density fat fraction (PDFF) technique, which has high accuracy and is strongly correlated with biopsy. However, the high cost of these methods and limited accessibility make them unsuitable as screening tools. Ultrasound (US) is considered the first-line imaging-based screening tool, given its lower cost and easier access. Although CT is not currently considered a screening tool for hepatic steatosis, it plays an important role in the opportunistic identification of hepatic steatosis due to its widespread use.

Source of the Paper

This paper was co-authored by Maryam Haghshomar, Dominic Antonacci, Andrew D. Smith, Sarang Thaker, Frank H. Miller, and Amir A. Borhani, from the Department of Radiology at Northwestern University Feinberg School of Medicine and the Department of Diagnostic Imaging at St. Jude Children’s Research Hospital. The paper was published in November 2024 in the journal Radiology.

Research Objectives

The primary objective of this study was to conduct a systematic review and meta-analysis to assess the accuracy of noncontrast CT (NCCT), contrast-enhanced CT (CECT), and dual-energy CT (DECT) in identifying at least moderate hepatic steatosis. The secondary objective was to determine reliable cutoffs for the commonly mentioned parameters in the literature.

Research Methods

Study Design

A systematic search of the PubMed, Embase, and Scopus databases was conducted, covering the period from September 1977 to January 2024, to identify studies evaluating the accuracy of CT in detecting hepatic steatosis. Inclusion criteria included studies that used biopsy or PDFF as the reference standard, as well as studies that used NCCT or CECT as the reference standard. Exclusion criteria included studies that did not provide original data, such as comments, editorials, news, guidelines, and reviews.

Data Extraction and Quality Assessment

Two researchers independently reviewed the search results to determine which articles to include for data extraction. The quality of each article was assessed using the modified Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Statistical analysis methods included a random-effects meta-analysis, assessment of heterogeneity using the I² statistic, and meta-regression to explore potential sources of heterogeneity.

Research Results

Diagnostic Accuracy of NCCT

A total of 23 studies involving 14,287 CT examinations were analyzed. NCCT had a sensitivity of 72% and a specificity of 88% for detecting any degree of hepatic steatosis (using biopsy or PDFF as the reference standard). For detecting at least moderate hepatic steatosis, NCCT had a sensitivity of 82% and a specificity of 94%.

Diagnostic Accuracy of CECT

Nine studies involving 3,958 CT scans were analyzed. CECT had a sensitivity of 66% and a specificity of 90% for detecting any degree of hepatic steatosis (using biopsy or PDFF as the reference standard). For detecting at least moderate hepatic steatosis, CECT had a sensitivity of 68% and a specificity of 93%.

Diagnostic Accuracy of DECT

Fewer studies were available for DECT, but it showed high sensitivity and specificity for detecting hepatic steatosis, at 85% and 88%, respectively.

Threshold Analysis

For NCCT, liver attenuation values of less than 40-45 HU, liver-spleen attenuation differences of less than -5 to 0 HU, and liver-to-spleen attenuation ratios of less than 0.9-1 achieved high specificity for detecting at least moderate hepatic steatosis.

Conclusion

This meta-analysis demonstrated that NCCT is a reliable method for detecting at least moderate hepatic steatosis. The use of liver attenuation values of less than 40-45 HU, liver-spleen attenuation differences of less than -5 to 0 HU, or liver-to-spleen attenuation ratios of less than 0.9-1 is recommended for detecting at least moderate hepatic steatosis. Although the initial results for CECT and DECT are promising, the existing evidence is insufficient to support their widespread use, and further research is needed.

Research Highlights

1. Key Findings: NCCT demonstrated high sensitivity and specificity for detecting at least moderate hepatic steatosis, at 82% and 94%, respectively.
2. Methodological Novelty: This study is the first to comprehensively evaluate the accuracy of NCCT, CECT, and DECT in detecting hepatic steatosis through a systematic review and meta-analysis.
3. Application Value: The study provides reliable CT thresholds for clinicians, aiding in the opportunistic detection of hepatic steatosis during widely used CT examinations, thereby enabling early intervention.

Research Significance

The scientific value of this study lies in providing reliable CT thresholds for the non-invasive diagnosis of hepatic steatosis, which has significant clinical application value. The results support the use of NCCT as an effective tool for detecting at least moderate hepatic steatosis and provide direction for future research on CECT and DECT.