Performance evaluation of an avian antibody-based particle-enhanced turbidimetric assay for free kappa and lambda light chains.

Quantification of serum free light chains (FLCs) is essential for the diagnosis and monitoring of plasma cell disorders. This study evaluated the analytical performance of a novel avian IgY-based particle-enhanced turbidimetric immunoassay (PETIA) for measuring free kappa (κ) and lambda (λ) light chains in serum and plasma. The assay was evaluated on the Cobas Pro c503 (Roche Diagnostics, Basel, Switzerland) and Abbott Architect c4000 (Abbott Laboratories, Abbott Park, IL) platforms using samples from patients with monoclonal components and healthy donors. Performance characteristics included precision, limit of quantification (LoQ), linearity, interference, measuring interval, reagent stability, high-dose hook effect, method comparison with the Diazyme FLC assay, and reference interval verification in 70 healthy individuals. Within-run precision was acceptable at clinically relevant concentrations. Functional LoQs (15% CV) were 1.94 mg/L for κ and 3.74 mg/L for λ. Linearity was demonstrated on the Abbott platform, with no significant interference from haemolysis, lipaemia or bilirubin. Reagents were stable for 38 days on-board, and no hook effect was observed at very high FLC concentrations. Method comparison showed strong correlation with the Diazyme assay (κ: r = 0.953; λ: r = 0.881) and substantial agreement for κ/λ ratios (Cohen's κ = 0.64). Verified reference intervals aligned with established standards. The IgY-based PETIA provides precise, interference-resistant measurement of free κ and λ light chains across a wide dynamic range, supporting its suitability for routine clinical use.