Adult liver recipients were randomized to standard practice ( control group ; n = 102 ) or serial immune function testing ( interventional group ; n = 100 ) performed with a commercially available in vitro diagnostic assay ( ImmuKnow ; Viracor-IBT Laboratories , Lee 's Summit , MO ) before transplantation , immediately after surgery and at day 1 , weeks 1 to 4 , 6 , and 8 , and months 3 to 6 , 9 , and 12 .