Abstract
Objective: Comparison of turbidimetric measurement of FLC concentrations by SpaPLUS (The Binding Site) and Immage 800 (Beckman Coulter), including index κ/λ, was the aim of this experiment. Materials and Methods: We simultaneously measured FLC-κ and FLC-λ concentrations in serum samples (n = 73) by Immage 800 and SpaPLUS.
We chose non-haemolytic samples with different FLC concentration, both from healthy probands, and from patients with MGUS (Monoclonal Gammopathy of Undetermined Significance) and MM (Multiple Myeloma). We calculated index κ/λ and statistically processed results.
We also measured FLC concentration in control samples and assessed repeatability and intermediate precision. Results: We found significant difference for FLC-κ, FLC-λ, and κ/λ ratio.
Concentrations measured by Immage 800 were generally lower in all parameters in comparison with SpaPLUS. FLC-κ difference was more pronounced than FLC-λ difference.
Minority of samples (n = 15), predominantly with high concentrations of FLC-κ, showed inversed trend and FLC-κ results were clearly higher when measured on Immage 800. Measurement precision (CV%) was slightly different in comparison to manufacturer's data, nevertheless satisfactory for clinical purposes.
Conclusion: Although we confirmed the expected difference of values measured by different devices, we do not consider the difference clinically relevant. We observed the shift in interpretation of κ/λ ratio using standard reference range (pathological value of κ/λ on the first analyzer, and κ/λ in reference range on second analyzer when measuring identical sample) only in limited number of cases.