Reuters Health Information (2013-08-22): Usual markers for NAFLD unreliable in black adolescents: study
Usual markers for NAFLD unreliable in black adolescents: study
Last Updated: 2013-08-22 17:40:15 -0400 (Reuters Health)
NEW YORK (Reuters Health) - Black adolescents may have non-alcoholic fatty liver disease (NAFLD) even in the absence of metabolic syndrome, and pediatricians need to bear that in mind when deciding who to screen, new research suggests.
In contrast to findings in other ethnic groups, metabolic syndrome (MetS) and insulin resistance performed poorly at identifying non-Hispanic black adolescents with elevated alanine aminotransferase (ALT) levels, study investigators say.
"The presence of metabolic syndrome may therefore not be an adequate trigger for NAFLD screening" in these youngsters, they wrote in a report online August 12th in Pediatrics.
Instead, triglyceride elevations, which performed similarly between groups in identifying ALT elevations, may be a better trigger for screening in young African-American patients.
The research team, led by Dr. Mark D. DeBoer at the University of Virginia in Charlottesville, analyzed data from 4,124 adolescents aged 12 to 19 who participated in the 1999 to 2010 National Health and Nutrition Examination Surveys.
NAFLD was presumed in patients with unexplained ALT elevations above 30 U/L. MetS was diagnosed based on a pediatric adaptation of the Adult Treatment Panel III.
Overall, 1,233 patients were non-Hispanic black, 1,207 were non-Hispanic white, and 1,684 were Hispanic. Patients with viral hepatitis were excluded, as were pregnant patients and anyone taking diabetic or lipid-lowering drugs.
The prevalence of elevated ALT varied, from 5.4% in non-Hispanic blacks, to 8.6% in non-Hispanic whites and 13.7% in Hispanics (p<0.0001).
Among whites and Hispanics, a classification of MetS helped identify adolescents with elevated ALT (odds ratios 9.53 and 5.56, respectively), as did MetS-related indices.
Among blacks, however, the association between MetS and ALT elevations was smaller and nonsignificant (OR, 3.24, p=0.051). Also, in this group, insulin resistance and a large waist circumference did not do as well to identify ALT elevations and may not be relatively good indicators for NAFLD for in these patients (ORs, 3.93 and 2.28, respectively, p<0.05).
Triglyceride elevation was a better predictor (OR, 4.44), the authors found. In email to Reuters Health, Dr. DeBoer said African-American adolescents with high triglycerides had an increase in risk of NAFLD similar to that seen in other ethnicities.
"NAFLD remains an important disease process with high prevalence in adolescence," Dr. DeBoer said. "Clinicians should have a high index of suspicion for NAFLD among obese adolescents with insulin resistance. Screening for ALT elevations among such children is warranted and may help target treatment earlier and prevent disease progression."
Triggers should include MetS among adolescents who are non-Hispanic white and Hispanic, he said.
But among African Americans, he added, "the presence of triglyceride elevations may be a particularly important trigger for NAFLD screening."
The findings support racial and ethnic differences in the link between MetS and NAFLD and a need for ethnic-based screening for adolescents at risk for NAFLD, the authors say.
"African Americans are both less likely to be diagnosed with the MetS and less likely to have NAFLD," Dr. DeBoer said. "These findings are interesting in that even when MetS is present, African-American adolescents are still less likely to have NAFLD than non-Hispanic white and Hispanic adolescents. Thus, there appears to be a curious dissociation between MetS, IR and NAFLD."
"We don't know why African Americans have this relative dissociation of IR and NAFLD," he added. "They have lower rates of high triglyceride in the first place, and the lower relationship between MetS and NAFLD in African-American adolescents may have similar underpinnings as the lower propensity to having high triglycerides."
Dr. Sonia Caprio, a pediatrician at the Diabetes Endocrinology Research Center at Yale University School of Medicine in New Haven, Connecticut, who wasn't involved in the study, commented in an email to Reuters Health that the relationships between insulin resistance and steatosis "are complex and not well understood."
"A major predictor of liver fat accumulation is the amount of visceral fat depot, which is notoriously small in African Americans," she said. "It remains unclear as to why this ethnic group presents with such distinct distribution of body fat and whether it has any relations to their propensity towards a greater degree of insulin resistance."