Platelet immuno-assay (PIA) as a simple and sensitive technique for the detection of antigens.

The platelet immuno-assay (PIA) is a simple and inexpensive technique to detect antigens with ng/ml sensitivity using micro-titer equipment and commercially available antisera. It can be easily adapted for virtually any antigen to which rabbit antiserum containing specific IgG-antibodies cna be obtained. The assay is inhibited by IgG and C1q in amounts greater than or equal to 125 microgram/ml and 12.5 microgram/ml respectively. Its application is thus limited to those fluids where IgG and C1q are present in less than these concentrations.