Development of Immunoturbidimetric Assays for Fourteen HumanSerum Proteins on the Hitachi 912

Many laboratories rely on dedicated nephelometers or turbidimeters and commercial reagent kits for the evaluation of serum proteins. However, with growing emphasis on cost containment, laboratories are forced to seek additional operational efficiencies by capitalizing on the use of existing analyzers whenever possible. In the present paper we describe the development of immunoturbidimetric assays for routine analysis of 14 human serum proteins (α1-antitrypsin, α2-macroglobulin, albumin, apolipoproteins AI and B, complement components 3 and 4, haptoglobin, immunoglobulins A, G, and M, orosomucoid, prealbumin, and transferrin) on the Hitachi 912™, a general chemistry analyzer. With this system, we obtained excellent precision at levels corresponding to low, normal, and high physiologic concentrations of each protein (within-run imprecision CVs ≤3.4%, total imprecision CVs ≤4.1%). Linearity for each method was within 5% of the expected value throughout the calibration range, and method comparisons with either the Roche turbidimetric or Dade Behring nephelometric assays were in good agreement (r >0.97). We observed no significant interference from bilirubin (up to 718 μmol/l), hemoglobin (up to 8 g/l), triglyceride (up to 14.7 mmol/l) or rheumatoid factor (up to 4140 IU/ml). Calibration for the 14 protein assays was stable for at least 7 days and onboard refrigerated reagents were stable for at least 3 months. The instrument's automated sample re-run feature minimized sample handling and helped to conserve specimens. In conclusion, the newly developed assays on the Hitachi 912™ offer high throughput (>250 tests per hour) without the associated cost of a dedicated instrument for protein assays.