Table 1.

Characteristics of the reference populations used to define the serum ALT ULN by 11 clinical laboratories.

Lab	N	Characteristics
A	Unknown	Reference range was determined long ago; as new instruments have been added, results always correlate, we continue to use this range
B	94	Excluded people with known medical conditions (e.g., hypertension, diabetes, heart disease, arthritis) or current medication use
C	100	Selected blood donors with no clinical symptoms
D	Unknown	Normal values have been the same for 25 years using the same instrument manufacturer; comparison studies between upgrades haves remained the same
E	Unknown	Excluded people with known medical conditions (e.g., hypertension, diabetes, heart disease, arthritis), current medication use, history of IV drug use
F	222	None
G	222	None
H	Unknown	Unknown criteria
I	> 120	Excluded people with known medical conditions (e.g., hypertension, diabetes, heart disease, arthritis), current medication use, history of IV drug use, and whose medical history would affect test results
J	1029	Excluded people with known medical conditions (e.g., hypertension, diabetes, heart disease, arthritis)
K	1354	Selected people with normal AST, alkaline phosphatase, bilirubin