Disease spectrum of abnormal serum free light chain ratio and its diagnostic significance

OBJECTIVE: To analyze the spectrum of abnormal serum free light chain ratio (sFLC κ/λ ratio), and to redefine the range of sFLC κ/λ ratio, so as to achieve hierarchical diagnosis of diseases with abnormal sFLC κ/λ ratio, resulting in the increased sensitivity and specificity in the diagnosis of monoclonal plasma diseases. METHODS: Enrolled 1,340 patients with abnormal sFLC κ/λ ratio (<0.26 or >1.65) were grouped: (1) group A: malignant plasma diseases; (2) group B: monoclonal gammopathies of undetermined significance (MGUS); (3) group C: reactive plasma diseases. These patients were further divided by renal function eGFR <60 or >60 ml/min/1.73m(2) to eliminate renal diseases influencing the results. Statistical analyses was performed by using SPSS 22 software. RESULTS: When sFLC κ/λ ratio >3.49 and eGFR >60ml/min/1.73m(2), the sensitivity and specificity of the diagnosis of malignant plasma diseases were 86.1% and 94.0%, respectively. When sFLC κ/λ ratio >2.89 and eGFR <60ml/min/1.73m(2), the sensitivity and specificity of the diagnosis of malignant plasma diseases were 92.0% and 97.0%, respectively. CONCLUSION: The sensitivity and specificity of the diagnosis of monoclonal plasma diseases can be significantly improved by redefining the cut-off value of sFLC κ/λ ratio and the renal function index of eGFR.