Table 6.

Examples of abnormal kappa/lambda free light chain (κ/λ FLC) ratios in patients tested for plasma cell disorders.

Disorder	SPEP (with IFE screening on all samples)			κFLC 3–19 (mg/L)	λFLC 6–26 (mg/L)	κ/λ FLC ratio 0.26–1.65	Reporting – Comment a
Renal failure	M-protein not detected. Inflammatory pattern. (eGFR 16 mL/min/1.73 m2)			120	69	1.74	The significance of a borderline high κ/λ FLC ratio in the presence of a marked increase in λ globulins or inflammatory response is uncertain.
T-cell leukaemia	M-protein not detected. Increased polyclonal IgG (28 g/L) and IgA (18 g/L). Inflammatory pattern. (CRP 84 mg/L)			190	110	1.75	It should not be regarded as diagnostic of a monoclonal light- chain disease.
Liver disease	Small low-level bands on polyclonal λ globulins. Their clinical significance is uncertain.			370	190	1.95	Suggest follow-up FLC.
Inflammatory bowel disease	M-protein not detected. Inflammatory pattern. (CRP 32 mg/L)			340	150	2.3	Borderline κ/λ FLC ratio; add generic comment a
CKD	M-protein not detected. Normal pattern. (eGFR 16 mL/min/1.73 m2)			100	48	2.1	κ/λ FLC ratios are reported to be as high as 3:1 in CKD.
NSMM	At diagnosis: M-protein not detected.			400	<4	>100	** Any calculated FLC ratio at this level of serum FLC is of uncertain significance. The κ/λ FLC ratio changes significantly with small changes in non-pathologic FLC.
	10 weeks post ASCT			7	11	0.64
	23 weeks post ASCT			<3	13	<0.23**
λ LCMM	At diagnosis monoclonal λBJP detected on SPEP
	β-globulins + λBJP: 24 g/L			8	57,000	<0.01
	18 months later λBJP not detected in serum but trace			280	160	1.75**	** NOTE: Original pathological FLC was λ light chain type.
	λBJP detected in urine on IFE.
κ LCDD	At diagnosis trace κBJP detected in urine on IFE
	No monoclonal band detected in serum; 23% plasma cells (κ light chain restricted on bone marrow trephine).			1200	19	63
	Pre ASCT: κBJP not detected; small bands on SPEP.			76	17	4.5
	8 weeks post ASCT: κBJP not detected; trace IgG λ bands – their clinical significance is uncertain.			4	64	0.06**	** NOTE: Original pathological FLC was κ light chain type.
	10 weeks post ASCT: κBJP not detected; small bands weakly present (probably transient).			9	11	0.82
MM (mainly λBJP with monoclonal IgA λ present in trace amounts in serum)	DATE	SPEP λBJP (mg/L)	UPEP λBJP (mg/24h)
	24.10.08 (presentation)	8,000	9,400	42	21,000**	0.002	** λFLC concentration by immunoassay was 3-to 4-fold higher than by SPEP over several samples.
	28.11.08	8,000	-	12	31,000**	<0.001
	Post treatment:						λBJP quantitated from SPEP was similar at presentation and 5 weeks later whereas λFLC concentration increased by ~ 50%.
	9.12.08	3,000	7,300	2	15,000	<0.001
	26.12.08	1,000	-	21	4,300	0.005
	12.1.09	Trace on IFE	-	14	580	0.02	Quantitation of low-level monoclonal bands (1–2 g/L) by scanning densitometry is prone to large imprecision.
	3.2.09	Trace on IFE	216	36	350	0.10
							However, trends in λFLC change were similar by both immunoassay and SPEP when monitoring this patient.

^aGeneric comment is ‘Increased serum FLC concentrations can occur not only when monoclonal light chains are present but also when immunoglobulin synthesis is elevated (e.g. autoimmune, liver and inflammatory diseases, infection), or immunoglobulin excretion is reduced (e.g. renal impairment).’

ASCT, autologous stem cell transplantation; BJP, Bence Jones protein; CKD, chronic kidney disease; CRP, C-reactive protein; eGFR, estimated glomerular filtration rate; IFE, immunofixation electrophoresis; LCDD, light chain deposition disease; LCMM, light chain myeloma; M-protein, monoclonal protein; NSMM, non-secretory myeloma; SPEP, serum protein electrophoresis; UPEP, urine protein electrophoresis.