Background: Specific proteins have traditionally been analyzed using methodologies such as immunonephelometry on specialized analyzers. It is now possible to perform specific protein testing on clinical chemistry analyzers using immunoturbidimetry. Performance characteristics of turbidimetric assays for eight common specific proteins were evaluated against a nephelometric method.
Methods: The Abbott Architect ci8200 and the Beckman Immage were used to perform IgA, IgG, IgM, C3, C4, haptoglobin, and transferrin testing. Abbott, Sentinel and Roche reagents were used to perform CRP testing on the ci8200. The specific protein assays were evaluated for precision, linearity, limit of detection, functional sensitivity, method comparison, prozone, and workflow.
Results: Total precision for the immunoturbidimetric assays was consistently better than 2% CV and linear throughout the dynamic range of the assays (recovery ± 10% of target values). The limits of detection, functional sensitivities, and accuracy (as determined by performance against target values for proficiency testing samples and reference materials) are suitable for clinical purposes. Method comparison, as determined by correlation coefficients, and performance against proficiency testing samples, demonstrated good agreement between the turbidimetric and nephelometric tests. Both the turbidimetric and nephelometric assays provided reliable results under conditions of antigen excess. Specific protein test requests could be consolidated within our routine chemistry workload without impacting analytical test throughput.
Conclusions: As demonstrated by their performance characteristics, the Architect ci8200 immunoturbidimetric specific protein assays are suitable for routine use and correlate well with representative immunonephelometric assays on the Beckman Immage analyzer. The ability to perform specific protein analyses on an integrated clinical chemistry/immunoassay system can allow for consolidation of testing on a single platform, resulting in improved laboratory operations efficiency.
