Clinical Utility of Serum Free Light Chain Assays in Multiple Myeloma: A 10-Year Multicentre Comparison with Serum Protein Electrophoresis in South-South Nigeria

Abstract

Background: In resource-limited settings, the diagnosis of multiple myeloma (MM) often relies on serum protein electrophoresis (SPE), which lacks sensitivity for light chain-only and oligo-secretory disease. This study evaluates the diagnostic utility of serum free light chain (sFLC) assays in a Nigerian cohort. Methods: This was a 10-year retrospective multicenter study of 67 patients diagnosed with MM in Port Harcourt, Nigeria. Clinical and laboratory parameters at diagnosis were analyzed. Renal function was assessed using estimated glomerular filtration rate (eGFR, CKD-EPI). Correlation between involved free light chains (iFLC) and renal function was evaluated. Results: The mean age was 55.9 ± 11.7 years, with a male-to-female ratio of 1.2:1. Bone pain (44.8%) and anemia (34.3%) were the most common presentations. SPE detected an M-protein in 68.7% of cases, while 31.3% were SPE-negative but sFLC-positive, representing a significant diagnostic gap. Over 50% of patients had renal impairment (eGFR <90 mL/min/1.73m²), with 17.9% having severe impairment (eGFR <40). Lambda-predominant disease was associated with significantly worse renal outcomes compared to kappa (p=0.019). A strong inverse correlation was observed between iFLC levels and eGFR (r = −0.68, p < 0.001). Conclusion: sFLC assays are indispensable for accurate diagnosis of MM in resource-limited settings, closing a critical diagnostic gap. Lambda light chain predominance was associated with more severe renal impairment and may serve as a prognostic marker.