Washington University in St. Louis, St. Louis, MO, USA.
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
Clin Chem Lab Med. 2023 Dec 5;62(5):929-938. doi: 10.1515/cclm-2023-0912. Print 2024 Apr 25.
Free light chain (FLC) assays and the ratio of κ/λ are recommended for diagnosis, prognosis and monitoring of plasma cell dyscrasias (PCD). Limited data exists on FLC clinical specificity in patients diagnosed with other conditions.
We assessed the κ, λ, and κ/λ FLC ratio using the FreeLite assay and the Sebia FLC ELISA assay in 176 patients with clinical presentations of fatigue, anemia, polyclonal hypergammaglobulinemia, joint disorders, kidney disease and non PCD-cancers with no monoclonal protein observed on serum protein electrophoresis or MASS-FIX immunoglobulin isotyping. Manufacturer defined reference intervals (RI) and glomerular filtration rate (GFR) specific RI (renal RI) were utilized.
For the κ/λ ratio, 68.7 % (121/176) of specimens on the FreeLite and 87.5 % (154/176) of specimens on the Sebia assay were within RI. For κ, 68.2 % (120/176) and 72.2 % (127/176) of results were outside RI for FreeLite and Sebia respectively. For λ, 37.5 % (66/176) and 84.1 % (148/176) of FreeLite and Sebia results were outside RI. With FreeLite and Sebia, patients with kidney disease (n=25) had the highest κ/λ ratios. 44 patients (25.0 %) had GFR <60 mL/min/BSA. When renal RI were applied, 13.6 % had a FLCr outside the renal RI with FreeLite, and 4.5 % with Sebia.
In a cohort of patients with signs and symptoms suggestive of PCDs, but ultimately diagnosed with other conditions, Sebia FLC had improved clinical specificity relative to FreeLite, if one was using an abnormal κ/λ ratio as a surrogate for monoclonality.
游离轻链（FLC）检测及其κ/λ比值推荐用于浆细胞异常疾病（PCD）的诊断、预后和监测。在诊断为其他疾病的患者中，关于 FLC 临床特异性的有限数据。
我们使用 FreeLite 检测和 Sebia FLC ELISA 检测评估了 176 例具有疲劳、贫血、多克隆高丙种球蛋白血症、关节疾病、肾脏疾病和非 PCD-癌症表现的患者的 κ、λ 和 κ/λ FLC 比值，这些患者的血清蛋白电泳或 MASS-FIX 免疫球蛋白分型无单克隆蛋白。使用制造商定义的参考区间（RI）和肾小球滤过率（GFR）特异性 RI（肾 RI）。
对于 κ/λ 比值，FreeLite 上的 176 个标本中有 68.7%（121/176）和 Sebia 上的 176 个标本中有 87.5%（154/176）在 RI 内。对于 κ，FreeLite 和 Sebia 的结果分别有 68.2%（120/176）和 72.2%（127/176）的结果超出 RI。对于 λ，FreeLite 和 Sebia 的结果分别有 37.5%（66/176）和 84.1%（148/176）超出 RI。使用 FreeLite 和 Sebia，患有肾脏疾病的患者（n=25）具有最高的 κ/λ 比值。44 名患者（25.0%）的肾小球滤过率（GFR）<60 mL/min/BSA。当应用肾 RI 时，FreeLite 有 13.6%的 FLCr 超出肾 RI，Sebia 有 4.5%的 FLCr 超出肾 RI。
在一组有 PCD 表现和症状但最终诊断为其他疾病的患者中，如果将异常 κ/λ 比值作为单克隆性的替代指标，那么 Sebia FLC 比 FreeLite 具有更高的临床特异性。
