Why assess GGT as well as %dCDT?
GGT and %dCDT are independent markers of heavy drinking. Alcohol may elevate one, the other or both in different people. It usually takes heavier and more chronic drinking to elevate GGT but in some people, especially women, GGT seems to be more sensitive to sub-acute heavy alcohol use. Also, GGT may increase secondary to other illnesses (ex. hepatic, biliary, obesity) and medications (ex. hormones, anticonvulsants). So if an isolated GGT is abnormal one might need %dCDT to confirm or disconfirm that the elevation is due to alcohol use.
