A comparative study of three approaches to the routine quantitation of human serum proteins

The Laser Nephelometer PDQTM (Hyland Division, Travenol Laboratories Inc.) and the Abbott Bichromatic Analyser 100 (Abbott Laboratories) were compared with a radial immunodiffusion method. Seventy-eight serum specimens collected during routine blood testing were aliquoted and quantitated by the three procedures described. The nephelometric system was used as described by Hyland in their instruction accompanying the LAS-R Nephelometric test kits. The ABA-100 was used with a filter unit transmitting at 340 and 650 nm and at a water bath temperature of 30 degrees C. The Laser Nephelometer correlated well with the RID system giving a correlation coefficient varying from 0.94 for IgA to 0.79 for C3. It was not possible to quantitate IgA by the turbidometric method using the ABA-100. Results obtained for the other proteins were satisfactory and the correlation coefficient with the RID method varied from 0.88 for IgG to 0.90 for C3. The RID procedure in routine use takes 5 hours technologist time and a 16-hour incubation period to produce results for IgG, IgA and IgM on nine patient specimens. Using the Laser Nephelometer to obtain the same results on 20 patient specimens took two to three technologist hours. Nephelometry, therefore, appears to be a satisfactory alternative to RID with a comparable precision and a great saving in technologist time.