Comparison of Measurement Free Light Chains by SPA_PLUS and Immage 80

Czech version

Authors: K. Bořecká ¹; P. Sečník ^2,3; A. Jabor ^2,3; J. Granátová ¹; M. Bolková ¹
Authors‘ workplace: Oddělení klinické biochemie, Thomayerova nemocnice, Praha ¹; Pracoviště laboratorních metod, IKEM, Praha ²; 3. lékařská fakulta UK, Praha ³
Published in: Klin. Biochem. Metab., 25, 2017, No. 3, p. 112-115

Overview

Objective:
Comparison of turbidimetric measurement of FLC concentrations by Spa_PLUS (The Binding Site) and Immage 800 (Beckman Coulter), including index κ/λ, was the aim of this experiment.

Design:

Settings:
Department of Clinical Biochemistry, Thomayer’s Hospital and Institute for Clinical and Experimental Medicine, Prague

Materials and Methods:
We simultaneously measured FLC-κ and FLC-λ concentrations in serum samples (n = 73) by Immage 800 and Spa_PLUS. 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 Spa_PLUS. 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.

Keywords:
Free Light Chains (FLC), κ/λ ratio, monoclonal gammopathy, turbidimetry.

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