[Two Serum Free Light Chain Detection Systems in the Diagnosis of Multiple Myeloma]

Objective: To investigate the comparability of the Freelite, Binding Site, Beckman and N Latex FLC, Siemens in the detection of serum free light chain (sFLC) .

Methods: Fifty newly diagnosed multiple myeloma (MM) patients in Tianjin Institute of Blood Research from November 2019 to February 2020 were enrolled. The two systems (Freelite, Binding Site, Beckman and N Latex FLC, Siemens) were used to detect the sFLC of the samples. Outlier detection was performed by ESD method, methodological comparison and deviation assessment were performed by Passing-Bablok regression and Bland-Altman regression.

Results: Both the systems could quantitatively analyze free kappa light chain serum samples and free lambda light chain samples. Freelite, Binding Site, Beckman and N Latex FLC, Siemens free light chain test showed FLC-κ：36.5 (6.5, 194), 40.5 (6.94, 288), FLC-λ: 30.1 (4.3, 170.5), 35.1 (2.28, 526), rFLC (FLC-κ/ FLC-λ) : 0.82 (0.05, 43.25), 1.03 (0.03, 32.04), dFLC (｜FLC-κ- FLC-λ｜) : -5.8 (-161.97, 183.7), 1.1 (-505.1, 279.01), which existed no outliers. There were systematic differences, and the deviation level was not within the clinically acceptable range.

Conclusion: Both the systems can meet the needs of clinical diagnosis and treatment, but there is a significant deviation between the two systems, the results are not comparable, and should be analyzed separately. In particular, the same system should be selected for monitoring the prognosis of MM.