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The sensitivity of current upper limit of normal of serum alanine aminotransferase (ALT) levels for detecting chronic liver disease has been challenged recently.
Dr Su and colleagues from Taiwan identified modulating factors for serum ALT levels, and refined its upper limit of normal threshold.
The research team enrolled 34,346 consecutive subjects who completed the health check-up at Taipei Veterans General Hospital from 2002 to 2009. Upper limit of normal was set for healthy ALT level to the 95th percentile of the reference healthy population.
A group of 21,282 subjects were used as a training set to define an upper limit of normal with the highest sensitivity.  | | Viral hepatitis is a major risk factor of elevated serum ALT levels | | Alimentary Pharmacology & Therapeutics |
Afterwards, this upper limit of normal was validated in another set of 13,064 subjects. A reference healthy population was selected from the training set after excluding subjects with any abnormalities in independent risk factors associated with elevated serum ALT level by multivariate analysis like body mass index, waist circumference, glucose, cholesterol, high-density lipoprotein-cholesterol, triglyceride, hepatitis B virus surface antigen, anti-hepatitis C virus antibody and fatty liver. The new upper limit of normal of serum ALT level defined as the 95% percentile in the healthy population were 21 IU/L and 17 IU/L for men and women respectively. The team noted that these cut-off values had the highest Youden's index and areas under the corresponding receiver operating curves among 4 widely applied thresholds in both the training and validation sets.
Dr Su's team concludes, "The suggested threshold of upper limit of normal provides better discrimination between healthy and unhealthy status." "Viral hepatitis, metabolic syndrome and fatty liver are the major risk factors of elevated serum alanine aminotransferase levels."
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