Department of Pathology, Medical College of Georgia at Augusta University, Augusta, GA, United States.
Department of Population Health Sciences, Medical College of Georgia at Augusta University, Augusta, GA, United States.
J Appl Lab Med. 2023 Nov 2;8(6):1101-1114. doi: 10.1093/jalm/jfad055.
The serum-free immunoglobulin light chain assay has been recommended as a screening test for monoclonal gammopathy. We evaluated the usefulness of urine free immunoglobulin light concentration for selection of specimens for immunofixation electrophoresis.
Using kits from The Binding Site for Freelite ®, we validated examination of urine for measuring free κ and λ light chains. The results of urine free light chain concentrations were evaluated to ascertain if the results could be used to reduce the number of specimens requiring urine protein immunofixation electrophoresis.
In the 515 specimens examined, there was no evidence of monoclonal gammopathy or history of monoclonal gammopathy in 331. Monoclonal κ or λ light chains were detectable in 42 and 30 specimens, respectively. There was history of κ or λ chain associated monoclonal gammopathy in 62 and 50 patients, respectively. In the 38 monoclonal κ positive urine specimens, with light chain data, κ/λ ratio was >5.83 in all specimens. In 27 specimens positive for monoclonal λ light chains, with light chain data, the urine λ/κ ratio was > 0.17 in 24 of 27 specimens and > 0.041 in all specimens. In patients without monoclonal gammopathy all specimens had a κ/λ ratio of >5.83 or λ/κ ratio >0.17.
The Freelite ® assay from The Binding Site is suitable for quantification of free light chains in urine. In patients with known history of monoclonal gammopathy, urine immunofixation electrophoresis may be omitted in specimens with κ/λ ratio of <5.83 for κ associated lesions and λ/κ ratio of <0.041 for λ associated lesions. However, the results do not support using this test for first-time urine testing for monoclonal light chains as it is not predictive of positive result, nor does it exclude a monoclonal light chain in urine.
无血清免疫球蛋白轻链检测已被推荐作为单克隆丙种球蛋白病的筛查试验。我们评估了尿游离免疫球蛋白轻链浓度在选择免疫固定电泳标本方面的有用性。
使用 The Binding Site 公司的 Freelite®试剂盒，我们验证了检测尿液中游离κ和 λ轻链的方法。评估了尿游离轻链浓度的结果，以确定其是否可用于减少需要进行尿蛋白免疫固定电泳的标本数量。
在检查的 515 份标本中，331 份无单克隆丙种球蛋白病或单克隆丙种球蛋白病史。分别在 42 份和 30 份标本中检测到单克隆 κ 或 λ轻链。分别有 62 份和 50 份患者有 κ 或 λ 链相关的单克隆丙种球蛋白病史。在 38 份单克隆 κ 阳性尿标本中，有轻链数据，所有标本的 κ/λ比值均>5.83。在 27 份单克隆 λ 轻链阳性标本中，有轻链数据，在 27 份标本中的 24 份中，尿 λ/κ比值>0.17，在所有标本中均>0.041。在无单克隆丙种球蛋白病的患者中，所有标本的 κ/λ比值均>5.83 或 λ/κ比值>0.17。
来自 The Binding Site 的 Freelite®测定法适用于定量检测尿液中的游离轻链。在已知有单克隆丙种球蛋白病史的患者中，对于 κ 相关病变的标本，κ/λ比值<5.83，以及对于 λ 相关病变的标本，λ/κ比值<0.041，可以省略尿免疫固定电泳。然而，该结果不支持将该试验用于首次检测尿中单克隆轻链，因为它既不能预测阳性结果，也不能排除尿中存在单克隆轻链。
