Original scientific paper

https://doi.org/10.11613/BM.2019.030709

Verification study of free light chains assays on reagent-optimized analysers

Dragana Šegulja ; Department of Laboratory Diagnostics, University Hospital Centre Zagreb, Zagreb, Croatia
Danica Matišić ; Department of Laboratory Diagnostics, University Hospital Centre Zagreb, Zagreb, Croatia
Karmela Barišić ; Department of Medical Biochemistry and Hematology, Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia
Dunja Rogić ; Department of Laboratory Diagnostics, University Hospital Centre Zagreb, Zagreb, Croatia

Abstract

Introduction: Our aim was to compare analytical specifications of two assays (monoclonal vs. polyclonal) for free light chains (FLCs) quantification
optimized for two different analytical platforms, nephelometer ProSpec (Siemens, Erlangen, Germany) and turbidimetric analyser Optilite (The Binding
Site, Birmingham, UK).
Materials and methods: The evaluation included verification of the precision, repeatability and reproducibility, estimation of accuracy and method
comparison study with 37 serum samples of haematological patients. Kappa and lambda FLC were measured in each sample by both methods
and kappa/lambda ratio was calculated.
Results: Results show satisfactory precision of both methods with coefficients of variation for ProSpec of CVwr = 2.20% and CVbr = 3.44%, and for
Optilite CVwr = 2.82% and CVbr = 4.15%. Estimated bias for FLC lambda was higher on the ProSpec analyser, but bias for FLC kappa was higher on the
Optilite analyser. Correlation coefficients were 0.98; P < 0.001 for FLC kappa and 0.97; P < 0.001 for FLC lambda. Considering normal/pathological
FLC ratio moderate agreement within assays was detected (κ = 0.621). When the results were categorized according to criteria for progressive disease,
4/37 (0.10) cases were differently classified. Lambda FLC values by Optilite in three samples with monoclonal FLC lambda were more than twelve
times higher than by ProSpec. A 25% difference in FLC ratio was detected in 16/37 (0.43) and 50% difference in 13/37 (0.35) patients.
Conclusions: All manufacturers’ precision claims could not be achieved in the verification study. The comparison of results to biological variations
data showed that coefficients of variations are acceptable for both assays. The assays should not be used interchangeably in haematological patients.

Keywords

M components; serum free light chains; immunoassay; gammopathy; monoclonal

Hrčak ID:

226456

URI

https://hrcak.srce.hr/226456

Publication date:

15.10.2019.

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