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Abstract
Background:
Since free light chain (FLC) is metabolized in the kidney, serum FLC concentration and kappa/lambda ratio are increased in patients with decreased renal function, even in the absence of monoclonal protein. In this study, we measured serum FLC levels to investigate the change in kappa/lambda ratios in relation to the severity of renal dysfunction. IFE) 등 전통적 검사방법과 기타 검사소견 및 임상소견, 영상소견
Results:
Serum FLC levels and kappa/lambda ratios increased depending on the severity of renal dysfunction. When patients were classified by setting cut-off value of eGFR as 60 mL/min/1.73 m2 (group A: eGFR ≥60 mL/min/1.73 m2, group B: <60 mL/min/1.73 m2), the kappa/lambda ratio of group B was significantly higher than that of group A (group B: 1.60±0.46 vs. group A: 1.35±0.27, P=0.018). Serum FLC kappa/lambda ratios were within the previously determined renal reference interval (0.37–3.1).
Conclusions:
When interpreting results of serum FLC kappa/lambda ratio, renal function status should be considered in addition to hematological findings. If renal function deteriorates, a wider renal reference interval is preferred instead of the usual reference interval.
Methods:
Serum FLC concentrations were measured in 92 archived serum samples from patients diagnosed with chronic kidney disease using the Freelite assay (The Binding Site Group Ltd., UK), and kappa/lambda ratios were calculated. Serum creatinine levels were assayed to calculate estimated glomerular filtration rate (eGFR), and patients were divided into subgroups according to Kidney Disease Improving Global Outcomes (KDIGO) guidelines. We analyzed the difference in serum FLC levels and kappa/lambda ratios between subgroups.
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Fig. 1.
Comparison of kappa/lambda ratio among patient groups according to severity of renal dysfunction. (A) Comparison between 4 groups divided by KDIGO guideline (group 2, mildly decreased; group 3, moderately decreased; group 4, severely decreased; group 5, kidney failure). (B) Comparison between two groups, group A (eGFR ≥60 mL/min/1.73 m2) vs. group B (eGFR <60 mL/min/1.73 m2). KDIGO represents Kidney Disease Improving Global Outcomes.
Table 1.
Demographic and laboratory characteristics of study population of patients with renal dysfunction (N=92)
Table 2.
Distribution of serum FLC and kappa/lambda ratio in patients with renal dysfunction
| Groups | Kappa FLC (mg/L) | Lambda FLC (mg/L) | Kappa/lambda ratio |
|---|---|---|---|
| Total (N=92) | 42.2 (15.9–277.0)∗ | 30.8 (12.8–202.0)∗ | 1.41 (0.66–2.90)∗ |
| G2 (mild kidney dysfunction) (N=25) | 24.0 (15.9–108.0)∗ | 18.0 (12.8–164.0)∗ | 1.32 (0.66–1.93)∗ |
| G3 (moderate kidney dysfunction) (N=44) | 42.4 (22.3–94.2)∗ | 30.2 (14.1–73.3)∗ | 1.40 (0.73–2.90)∗ |
| G4 (severe kidney dysfunction) (N=14) | 84.7 (36.5–165.9)∗ | 51.3 (30.9–77.0)∗ | 1.77 (0.91–2.46)∗ |
| G5 (kidney failure) (N=9) | 119.7 (63.3–277.0)∗ | 58.5 (39.9–202.0)∗ | 1.86 (1.21–2.55)∗ |
| Reference interval (Katzmann et al. [10]) | 3.3–19.4† | 5.7–26.3† | 0.59 (0.26–1.65)∗ |
| Renal reference interval (Hutchison et al. [9]) | 43.8 (3.0-251.0)∗ | 38.0 (1.0-251.0)∗ | 1.1 (0.37–3.1)∗ |
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