The Impact of a Heterozygous SLCO1B3 Null Variant on the Indocyanine Green Retention Test

Indocyanine green (ICG) retention test is widely used for preoperative evaluation of liver function. OATP1B3 (gene symbol: SLCO1B3) is the major transporter for hepatic ICG uptake. We previously demonstrated that the individuals with a homozygous SLCO1B3 null allele revealed markedly impaired ICG clearance. However, the effect of heterozygosity of this variant on ICG clearance remains unknown. We compared the results of ICG retention rate at 15 min (ICG-R15) and hepatic OATP1B3 expression among individuals whose SLCO1B3 genotype was determined. Although OATP1B3 expression was significantly lower in the heterozygosity than the wild-type, the ICG-R15 results were comparable; 8.4 ± 3.4 (mean ± SD) % in the heterozygosity and 8.7 ± 6.0% in the wild-type. A homozygous individual revealed markedly high ICG-R15 (79.8%) and lacked OATP1B3 expression. In conclusion, the individuals with a heterozygous SLCO1B3 null variant had similar ICG clearance capacity to those with the wild-type despite decreased hepatic OATP1B3 expression.