Patent ID: 8728800

Claim:
A method of assaying for plasma homocysteine in a whole blood sample taken from a human or vascularized non-human animal subject, said method comprising: contacting a whole blood sample from said subject with the following reagents—a liquid diluent, a reducing agent, a homocysteine-converting enzyme, an inhibitor of the homocysteine converting reaction of said enzyme, adenosine or an adenosine analog as homocysteine co-substrate, a cell-lysing agent, a color-labeled binding agent comprising an anti-S-adenosyl-homocysteine (SAH) antibody capable of binding to a conversion product of said homocysteine-converting enzyme, and a particulate comprising polymer particles conjugated to S-adenosyl cysteine capable of competing with said conversion product for binding to said color-labeled binding agent; following contact with said reagents, drawing said sample through a membrane having a porosity sufficient to allow passage therethrough of said color-labeled binding agent in its unbound state and when bound to said conversion product but insufficient to allow passage therethrough of said color-labeled binding agent when bound to said particulate; detecting the color-label of said color-labeled binding agent retained on said membrane; determining therefrom an indication of the plasma homocysteine concentration by applying a correction factor dependent on red blood cell concentration in said whole blood sample; and optionally presenting the plasma homocysteine concentration as a visible or electronic signal; wherein contact with said reagents is sequential or simultaneous subject to the provisos that: i) contact with said color-labeled lysing agent occurs after contact with said diluent, enzyme and reducing agent; ii) contact with said color-labeled binding agent and said particulate does not involve contact with a liquid containing both said color-labeled binding agent and said particulate; and iii) contact with said inhibitor occurs after contact with said diluent, enzyme and reducing cell agent and no later than contact with said cell lysing agent.