When many samples have to be analysed,many laboratories employ more sophisticated instrumental techniques such as turbidity and nephelometry and these quantitative immunoprecipitin techniques in a fluid medium are routinely applied for the measurement of albumin,IgG,IgM,IgA and IgD,fibrinogen and complement components among others. In these techniques,monochromatic light is passed through a solution of antigen with antibody and the amounts of complexes formed are measured by either the amount of light scatter or light absorption. The latest instrument s use laser technology and can detect nanogram quantities of antigen-antibody complexes.