Quantitative nephelometric determination of Haemophilus influenzae antigen in body fluids.

Nephelometry, an immunological technique widely used for the quantification of blood proteins, was adapted to provide a quantitative method of detecting Haemophilus influenzae capsular antigen in body fluids. Using specific antiserum directed against H. influenzae capsular antigen, samples of serum, cerebrospinal fluid, urine, and joint fluid from 38 cases of H. influenzae infections were analyzed. The results were compared for reliability to counterimmunoelectrophoresis, a widely used diagnostic tool. The nephelometric technique has the same advantages of speed and specificity as counterimmunoelectrophoresis and provides the clinician and researcher with a quantitative method that is as reliable as the qualitative counterimmunoelectrophoresis procedure. The method allowed directly quantitative readouts on patient specimens, with no necessity for serial dilutions or densitometric readings.