. 2019 Feb;40(1):5–22.

Table 9.

Current serum free light chain assays and manufacturers’ specifications.

Assay	Antibody (anti-κ + λ)	Method	Platform(s)	Clinical validations	Reference interval(s)	Precision: CV (%) over measuring range
Freelite® (Binding Site Group)	Polyclonal antibodies (sheep): latex conjugates	INA, ITA	Protein and multiple automated (antigen excess testing is not available on all platforms)	AL amyloidosis, MM (including NSMM, LCMM, intact Ig MM), AKI, ESRF, WM, CLL, polyclonal immunoglobulin disorders	k FLC 3.3–19.4 mg/L l FLC 5.7–26.3 mg/L FLC ratio 0.26–1.65⁵³ FLC ratio 0.37–3.1 (ESRF)⁵⁴ Involved FLC >500 mg/L (AKI)⁵⁵	<20%⁵⁶
N-Latex (Siemens)	Monoclonal antibodies: polystyrene-conjugates	INA	BN Systems (antigen excess testing provided)	AL amyloidosis, MM (including NSMM, LCMM, intact Ig MM), ESRF	k FLC 6.7–22.4 mg/L l FLC 8.3–27.0 mg/L FLC ratio 0.31–1.56⁵⁷ k/l FLC ratio 0.31–1.56 (ESRF)⁵⁸	<5–7%⁵⁹
Seralite and ELISA (Abingdon)	Monoclonal antibodies: gold-labelled	1. Competitive inhibition	1. Cartridge & reader device (lateral flow technology)	MM (including NSMM, LCMM, intact Ig MM), AKI	k FLC 5.2–22.7 mg/L l FLC 4.0–25.1 mg/L FLC ratio 0.5–2.5⁵⁹ FLC ratio 0.5–2.5 (ESRF)⁶⁰	9–12% (2 batches of cartridge, 60 devices, 3 operators)⁵⁹
		2. ELISA	2. ELISA		FLC ratio 0.14–2.02; dFLC ≥400 mg/L (AKI)⁶¹
SebiaFLC (Sebia)	Polyclonal antibodies (rabbit): latex-enhanced	ELISA	ELISA (AP22 ELITE); Assay can be adapted to other ELISA platforms	MM	k FLC 5.2–15.3 mg/L l FLC 8.2–18.1 mg/L FLC ratio 0.37–1.44⁶² FLC ratio 0.46–2.23 (ESRF)⁶³	k FLC: 1.9–7.6% (between day) l FLC: 6.0–6.3% (between day)⁶²

AKI, acute kidney injury; CLL, chronic lymphatic leukaemia; ESRF, end-stage renal failure; FLC ratio, kappa/lambda free light chain ratio; INA, immunonephelometric assay; ITA, immunoturbidimetric assay; intact Ig MM, intact immunoglobulin myeloma; LCMM, light chain myeloma; MM, multiple myeloma; NSMM, nonsecretory myeloma; WM, Waldenström macroglobulinaemia