Performance and clinical evaluation of two serum free light chain detection platforms in the diagnosis of multiple myeloma / 中华检验医学杂志

ABSTRACT

Objective:To compare the detection performance of serum free light chain (sFLC) in two platforms and evaluate the comparability of serum free light chain results in patients with multiple myeloma (MM).Methods:To evaluate the detection performance (repeatability, accuracy, linear range, reference range, interfering substances, etc.) of sFLC kit based on polyclonal antibodies. Spearman correlation analysis and Bland-Altman were used to analyze 214 sFLC results obtained on two detection platforms at the same time to evaluate the correlation between the results of the two methods and analyze the causes of methodological bias. 119 cases with aMM and 23 cases of disease control group (AL, WM, POEMS syndrome, MGUS, diffuse large B-cell lymphoma) initially diagnosed in the hematology department of Zhongshan Hospital of Fudan University from March 2020 to March 2021 were all included. A retrospective analysis was conducted to calculate the area under the curve of receiver operating characteristic (AUC-ROC) and obtain the optimal sensitivity and specificity cut-off points for the diagnosis of MM patients on monoclonal antibody platform.Results:Repeatability, accuracy, linear range, reference interval and anti-interfering capacity of the detection platform based on polyclonal antibodies were verified to meet clinical needs. The overall consistency of FLC/κ, FLC/λ and κ/λ ratios in two methods was 89.3%, 84.1% and 77.1% respectively; but the correlation results were highly heterogeneous. The correlation coefficient of FLC/κ R 2 was 0.922( P<0.001), while the correlation coefficients R 2of the FLC/λ and κ/λ ratios were only 0.349 and 0.441( P<0.001). After segment analysis, it was found that the correlation of FLC/λ was improved within the linear range and R 2 could rise to 0.78( P<0.001). Compared with monoclonal antibody platform, the vast majority points of FLC/κ fell within the 95% limit by Bland Altman analysis. While the results of FLC/λ on polyclonal antibody platform showed significant positive bias. The AUC of MM diagnosis on monoclonal antibody platform was 0.751 ( P=0.001), and the optimal cutoff value was 24.67. Conclusion:The overall consistency between the two platforms was good, but there were significant differences between the results, so they were not comparable and could not be interchanged. For monitoring the prognosis of patients with multiple myeloma, the same platform should be selected for testing.