Research ArticleDevelopment and validation of a new histological score for pediatric non-alcoholic fatty liver disease
Introduction
Pediatric NAFLD encompasses a wide spectrum of disease ranging from hepatic steatosis characterized by hepatic lipid accumulation in the form of triglyceride (TG), to non-alcoholic steatohepatitis (NASH) characterized by the association of lipid accumulation with evidence of hepatocyte injury, inflammation, and various degrees of fibrosis to advanced fibrosis and cirrhosis [1], [2], [3]. Currently, a liver biopsy remains the gold standard to distinguish NASH from simple steatosis and establish the extent of liver damage and fibrosis [4].
Since the initial description by Ludwig et al., the histological criteria for diagnosing NASH have been evolving and several grading and staging systems have been proposed to assess the histologic severity of the disease [5], [6], [7]. The NAFLD activity score (NAS) was developed by the National Institute of Diabetes and Digestive and Kidney Diseases NASH Clinical Research Network (CRN) [8]. The score is based on the classification proposed earlier by Brunt et al. [5] and consists of the unweighted sum of scores for each of the following lesions: steatosis, hepatocyte ballooning, and lobular inflammation. This semiquantitative score was specifically developed for the assessment of response to therapeutic intervention. In children, it was based on a total of 18 cases that were each read once by nine pathologists for a total of 162 sets of observations [8]. Since the development of the original NAS, it has become evident that pediatric NASH may present with a distinct histopathological pattern characterized mainly by the presence of portal-based disease including portal inflammation (PI) [9], [10], [11]. Indeed, we and others have demonstrated that PI may represent an important feature of more severe disease in children with NASH [9], [11], [12]. In addition, some histological features are more indicative of the presence of NASH and should carry more weight when developing a histological score to identify patients for enrollment in therapeutic trials. For example, hepatocyte ballooning is a major distinguishing feature of NASH that confers an increased risk of disease progression [13]. The importance of ballooning has been emphasized by the results of the two largest randomized trials for NAFLD treatment in adults and children, namely the PIVENS and TONIC trials [14], [15].
As a result of these issues, when NAS is applied to the pediatric population, typically, only about half of patients can be categorized into a clear-cut pattern while the other half fall into the “borderline” category, supporting the need for a more reproducible scoring system to interpret liver histology in pediatric cases of NAFLD. This score should allow for a better separation of cases into clear-cut meaningful categories that would greatly facilitate inclusion and risk stratification of patients in therapeutic and diagnostic trials. Thus, the aim of this study was to develop and validate a new grading score for pediatric NAFLD that takes into account the presence of PI and the weight of each histological feature and to examine the level of agreement between this score and the pathologist diagnostic determination of NASH.
Section snippets
Study population
A total of 303 consecutive children with biopsy-proven NAFLD were included in this study. The study was approved by the Ethics Committee of the Bambino Gesù Children’s Hospital and Research Institute, Rome, Italy. Informed consent was obtained from each patient or responsible guardian. Inclusion criteria were persistently elevated serum aminotransferase levels, diffusely hyperechogenic liver on ultrasonography suggestive of fatty liver, and biopsy consistent with the diagnosis of NAFLD.
Patient characteristics
The main clinical and laboratory characteristics of the initial set of patients (n = 203) used to develop the new histological score are summarized in Table 1. The median age of the patients at the time of diagnosis was around 12 years and was not different between patients with or without NASH. Subjects with NASH were found to have significantly greater WC, higher WC percentile, WC/height ratio, total cholesterol, triglyceride levels and gamma glutamyl transferase (GGT), lower total bilirubin and
Discussion
The main finding of our study relates to the development and validation of a new histological score, the PNHS, to categorize NAFLD into NASH and “not NASH” for inclusion in pediatric clinical trials. Avoiding the “borderline NASH” category will allow for a better classification of children into groups with or without NASH. Our results demonstrated that: (1) there is a high level of agreement between categorization of NAFLD cases using PNHS and the pathologist’s diagnosis, (2) a PNHS of ⩾85 can
Financial support
Supported by grants from “Bambino Gesù” Children’s Hospital and Research Institute, Rome, Italy.
Conflict of interest
The authors who have taken part in this study declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.
References (31)
- et al.
Non-alcoholic steatohepatitis: a proposal for grading and staging the histological lesions
Am J Gastroenterol
(1999) - et al.
Hepatocellular ballooning in NASH
J Hepatol
(2010) - et al.
Waist circumference percentiles in nationally representative samples of African–American, European–American, and Mexican–American children and adolescents
J Pediatr
(2004) - et al.
The natural history of non-alcoholic fatty liver disease: a population-based cohort study
Gastroenterology
(2005) - et al.
Non-alcoholic fatty liver disease: a spectrum of clinical and pathological severity
Gastroenterology
(1999) - et al.
NASH and cryptogenic cirrhosis: a histological analysis
Ann Hepatol
(2009) Non-alcoholic fatty liver disease
N Eng J Med
(2002)- et al.
Pathological features of NASH
Front Biosci
(2005) - et al.
The natural history of non-alcoholic fatty liver disease in children: a follow-up study for up to 20 years
Gut
(2009) - et al.
Diagnosis of non-alcoholic fatty liver disease: invasive versus noninvasive
Semin Liver Dis
(2008)
Non-alcoholic steatohepatitis: Mayo Clinic experiences with a hitherto unnamed disease
Mayo Clin Proc
Proposal for a histological scoring and grading system for non-alcoholic fatty liver disease
Liver Int
Design and validation of a histological scoring system for non-alcoholic fatty liver disease
Hepatology (Baltimore, MD)
Non-alcoholic steatohepatitis in children: a multicenter clinicopathological study
Hepatology (Baltimore, MD)
Clinical correlates of histopathology in pediatric non-alcoholic steatohepatitis
Gastroenterology
Cited by (75)
Fatty Liver Disease
2023, MacSween's Pathology of the Liver, Eighth EditionNon-alcoholic fatty liver disease in children and young adults is associated with increased long-term mortality
2021, Journal of HepatologyCitation Excerpt :The histological spectrum of NAFLD ranges from simple steatosis to inflammatory steatohepatitis (NASH) which can progress to fibrosis and cirrhosis.3,4 While the classic form of adult NASH is marked by hepatocyte ballooning with zone 3 lobular inflammation and collagen deposition, some pediatric patients develop a distinct form of NASH, characterized instead by zone 1 inflammation without ballooning, and with portal or periportal fibrosis.3,4 Among adults, longitudinal studies have demonstrated that simple steatosis typically follows a relatively benign disease course, whereas NASH with fibrosis is associated with an increased risk of death.5–7
Nonalcoholic Fatty Liver Disease in Children: Unique Considerations and Challenges
2020, GastroenterologyCitation Excerpt :Ballooning degeneration, absent in type 2 NASH, confers an increased risk of disease progression in adults, although as an individual pathologic feature, it is not an independent predictor of outcome.19 Although degree of fibrosis serves as a prognostic marker in adult NASH, lack of longer-term natural history studies in pediatrics precludes the determination of whether patients with the pediatric pattern differ in etiopathogenesis, prognosis, or response to treatments targeting specific pathways (Table 1).20 Children with NAFLD have varying degrees of disease severity at time of diagnosis.
Nonalcoholic Fatty Liver Disease
2020, Pediatric Gastrointestinal and Liver Disease, Sixth EditionPrevalence of prediabetes and diabetes in children and adolescents with biopsy-proven non-alcoholic fatty liver disease
2019, Journal of HepatologyCitation Excerpt :The assignment of NASH, borderline NASH, or NAFLD without NASH was always confirmed by an expert liver pathologist. In this study, a different grading histologic score for pediatric NAFLD was also used to test the reproducibility of our original results, i.e., the Pediatric NAFLD Histological Score (PNHS),19 which is calculated by using the weighted sum of hepatic steatosis, ballooning, lobular inflammation and portal inflammation, according to the following formula: PNHS = 100 × exp (zPNHS)/[exp(zPNHS)], where zPNHS = −8.4 + 2.5 × steatosis + 3.5 × ballooning + 3.4 × lobular inflammation + 0.87 × portal inflammation. Blood samples were collected and the genomic DNA was extracted by QIAamp Blood MiniKit (Qiagen, Hilden, Germany), according to the manufacturer’s instructions.