The amount of a orphan sodium- and chloride-dependent neurotransmitter transporter NTT5 when measured in blood serum. The trait is level of orphan sodium- and chloride-dependent neurotransmitter transporter NTT5 in blood serum (OBA_2043541, an Ontology of Biological Attributes entry). Also known as: blood serum orphan sodium- and chloride-dependent neurotransmitter transporter NTT5 amount.