The amount of a all-trans-retinol dehydrogenase [NAD(+)] ADH4 when measured in blood serum. The trait is OBA_2040516 (level of all-trans-retinol dehydrogenase [NAD(+)] ADH4 in blood serum). Also known as: blood serum all-trans-retinol dehydrogenase [NAD(+)] ADH4 amount.