“…(2) In most previous studies, there are exclusions of patients with liver disease (Anton et al, 2002;Chen et al, 2003;Harasymiw et al, 2004;Mundle et al, 2000;Reynaud et al, 2000), patients on medications that affect the hepatic system (Mundle et al, 1999b(Mundle et al, , 2000Myrick et al, 2001;Sillanaukee et al, 2000aSillanaukee et al, , 2000b, or patients who are pregnant (Anton et al, 2002;Reynaud et al, 2000;Sillanaukee et al, 2000aSillanaukee et al, , 2000b. Although the potential impairment of the enzyme system is a logical reason for exclusion, those studies with exclusions cannot claim either a representative sample or a more realistic estimation of the practical use of the markers.…”