The amount of a potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 1 when measured in blood serum. The trait is Ontology of Biological Attributes entry OBA_2040220 (level of potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 1 in blood serum). Also known as: blood serum potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 1 amount.