Gender and age were equally distributed between wild-type group (wt/wt) and heterozygous CCR-5��32 group (wt/��32). Patients in the homozygous group (��32/��32) were female and male. The observed genotype frequency was as expected assessed by Hardy-Weinberg equilibrium in the study population. There were no differences between wt/wt group and wt/��32 group regarding to CPS score, Diabete MELD score or blood group (Table 1). Table 1 Recipient characteristics. MELD: model for end-stage liver disease; CPS: Child-Pugh score; BG: recipients blood group; wt/wt: wild-type CCR-5; wt/��32: heterozygous CCR-5��32; ��32/��32: homozygous CCR-5��32; CMV: cytomegalovirus; … There were no statistical significant differences in the composition of underlying liver disease of group wt/wt and wt/��32.

Both patients with ��32/��32 had primary biliary cirrhosis as underlying liver disease. Initial immunosuppression was tacrolimus based in 82.6% in the wt/wt group compared to 84.8% in the wt/��32 group. Likewise, cold ischemic time and HLA match showed no differences between groups. Both homozygous ��32 patients had zero HLA match. CMV infection that demanded ganciclovir treatment was present in approximately 30% in the wt/wt and wt/��32 group and in both homozygous patients. 6.2. Donor Characteristics There were no differences between group regarding donor age or gender. Donors of group ��32/��32 were younger (35.7 years versus 46.5 years and 48.5 years). Mean donor serum sodium was 146.9 mmol/L in the wt/wt group compared with 147.7 mmol/L in the wt/��32 group and 155.5 mmol/L in the ��32/��32 group.

Data of causes of brain death and length of stay on the ICU prior to organ harvesting are shown in Table 2. Table 2 Donor characteristics. ICU: intensive care unit; wt/wt: wild-type CCR-5; wt/��32: heterozygous CCR-5��32; ��32/��32: homozygous CCR-5��32. 6.3. Incidence ITBL and Rate of Retransplantation Incidence of ITBL was 11.2% in this study due to the selection of patients with ITBL that were additionally included into this evaluation. Homozygous ��32 patients developed no ITBL compared to 11.2% and 12.1% of homozygous wild-type patients and heterozygous patients, respectively. The rate of retransplantation was 3.0% in both wt/wt and wt/��32 group (see Table 3). Retransplantation of the heterozygous patient was indicated due to chronic ductopenic rejection following OLT for PSC.

In the wt/wt group, the indications for retransplantation were INF, cryptogenic recirrhosis, and ITBL. Table 3 Events after transplantation. wt/wt: wild type CCR-5; wt/��32: heterozygous CCR-5��32; ��32/��32: homozygous CCR-5��32; ITBL: ischemic-type biliary lesion; Re-OLT: retransplantation. 7. Discussion The problem of genetic Drug_discovery association studies and complex clinical syndromes or diseases must be addressed. One can always question the usefulness of these studies that are often even small in sample size. Most of these studies are statistically underpowered.