Citation: Annals of Clinical Biochemistry. 2015 Nov 13
Author: Galvani L, Flanagan J, Sargazi M, Neithercut WD
Abstract: BACKGROUND: The demand for measurement of serum immunoglobulin free kappa (κ) and lambda (λ) light chains has increased. The κ:λ ratio is used to assist in diagnosis/monitoring of plasma cell disorders. The Binding Site reference range for serum free light chain (FLC) κ:λ ratios of 0.26-1.65 was derived from healthy volunteers. Subsequently a reference range of 0.37-3.1 for patients with chronic kidney disease (CKD) has been proposed. Elevated FLC concentrations and borderline raised FLC ratios also may be found in polyclonal gammopathies and with other non-renal illnesses. This assessment was conducted to validate the established FLC reference ranges in individuals from primary care.
METHOD: A total of 130 samples were identified from routine blood samples collected in primary care for routine biochemistry testing and eGFR calculation.
RESULTS: The median and range of κ:λ ratios found in each eGFR group used for CKD classification was higher than previously described. This was the case for individuals with normal or essentially normal renal function with eGFRs > 90, (0.58-1.76) and eGFR of 60-90 mL/min/1.73m2, (0.71-1.93). Individuals with eGFR 15-30, (0.72-4.50) and eGFR <15ml/min/1.73m2 (0.71-4.95) also had higher values when compared to the current renal reference range of 0.37-3.10.
CONCLUSIONS: Elevation of FLC-κ:λ ratios may occur in the absence of a reduced renal function shown by a normal eGFR and in the presence of reduced renal function by eGFR when comparing results with the established reference ranges. Explanations include choice of analytical systems or the presence of other concurrent non plasma cell illness
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