Using Two Detection Methods to Observe the Changes and Significance of Free Light Chain in Serum and Urine in Patients with Renal Insufficiency

BACKGROUND: Free light chains κ and λ (FLC κ, FLC λ) are of great significance in diagnostic and monitoring monoclonal gammopathy. Freelite and N-Latex methods are two common monitoring methods at present. But the two meanings are not completely equivalent, especially for patients with renal insufficiency. We analyzed the changes of serum and urine FLC in renal insufficiency patients without monoclonal gammopathy and the clinical significance of these changes. METHODS: This study is an observational study. Patients ≥ 18 years old, who met the diagnostic criteria of chronic kidney disease (CKD), excluding monoclonal gammopathy, were selected. Fasting serum and 24-hour urine were taken to detect serum FLC κ, serum FLC λ, SCr, serum β(2)-microglobulin, urinary FLC κ, urinary FLC λ, urinary α(1)-microglobulin, and urinary β(2)-microglobulin. RESULTS: There was a good correlation between the two methods for determining serum/urinary FLC. No matter serum or urine, FLC showed a good correlation with renal function by the N-Latex method, but not by the Freelite method. Under the N-Latex method, FLC κ/λ remained stable, which was basically within the reference range of healthy people and was not affected by renal function. There was a good correlation between FLC detected by N-Latex and microglobulin in serum and urine. CONCLUSION: When the concentration of FLC is low, the N-Latex method is more recommended to monitor FLC. The FLC measured by the N-Latex method is more closely related to renal function. The ratio of FLC κ/λ determined by the N-Latex method remained stable within the recommended range.