First definition of reference intervals of liver function tests in China: a large-population-based multi-center study about healthy adults.

Background: Reference intervals of Liver function tests are very important for the screening, diagnosis, treatment, and monitoring of liver diseases. We aim to establish common reference intervals of liver function tests specifically for the Chinese adult population.

Methods: A total of 3210 individuals (20-79 years) were enrolled in six representative geographical regions in China. Analytes of ALT, AST, GGT, ALP, total protein, albumin and total bilirubin were measured using three analytical systems mainly used in China. The newly established reference intervals were based on the results of traceability or multiple systems, and then validated in 21 large hospitals located nationwide qualified by the National External Quality Assessment (EQA) of China.

Results: We had been established reference intervals of the seven liver function tests for the Chinese adult population and found there were apparent variances of reference values for the variables for partitioning analysis such as gender(ALT, GGT, total bilirubin), age(ALP, albumin) and region(total protein). More than 86% of the 21 laboratories passed the validation in all subgroup of reference intervals and overall about 95.3% to 98.8% of the 1220 validation results fell within the range of the new reference interval for all liver function tests. In comparison with the currently recommended reference intervals in China, the single side observed proportions of out of range of reference values from our study for most of the tests deviated significantly from the nominal 2.5% such as total bilirubin (15.2%), ALP (0.2%), albumin (0.0%). Most of reference intervals in our study were obviously different from that of other races.

Conclusion: These used reference intervals are no longer applicable for the current Chinese population. We have established common reference intervals of liver function tests that are defined specifically for Chinese population and can be universally used among EQA-approved laboratories located all over China.