Immunoassay with solid phase having coating containing blood platelet substitute

A method for preparing an immunologically active coated solid phase by coating the surface of a solid support material having an organic polymer surface with an immunologically active agent which comprises the steps of:

• (a) contacting the organic polymer surface of the solid support material with an aqueous coating solution having a pH-value of from about 8.5 to about 10.5 and comprising dissolved therein an amount of from about 0.035 to about 0.05 mol/l of a water soluble protein-compatible primary or secondary hydroxy lower alkyl amine, an amount of between 0.05 and about 20 g/l of a water/soluble immunologically active agent and an amount of from about 0.05 to about 10 g/l of a blood platelet substitute which is a brain extract containing phospholipids and cephalin for a sufficient period of time to allow an immunologically effective amount of the immunologically active agent to be attached to the organic polymer surface of the solid support material to obtain an immunologically active coating therein,
• (b) removing the coating solution from the coated solid support material
• (c) allowing the coated solid support material to dry.