Serum free light chain ratio predicts outcome in MGUS

C ancer Prognosisas published in CLI December 2005Table 2. Reference ranges for serum free kappa and lambda light chains.abnormal free light chain ratio (kappa/lambda1.65) [Table 2] was detected in 379(33%) patients. This group had a significantlyhigher risk of progression compared to those witha normal κ/λ ratio [Figure 2], (hazard ratio, 3.5;95% confidence interval, 2.2 - 5.5; P 50 years) as part of an epidemiologicalstudy [12]. These were selected on thebasis of negative serum protein electrophoresis(SPE). When assessed for serum free light chains12 of the samples were abnormal. These 12 serawith abnormal κ/λ ratios were carefullyreassessed by immunofixation electrophoresis. Ofthese, it is likely that 7 had detectable monoclonalfree light chains, possibly representing a previouslyunknown entity of free light chain MGUS.Two patients with intact immunoglobulin M proteinsmissed in the original SPE tests were identifiedby the serum free light chain assays.Long term follow-up studies are needed to determinethe significance of free light chain MGUS, tosee whether these patients progress to light chainmultiple myeloma or if the risk of progression isFigure 2. Risk of progression in patients with normal and abnormal κ/λ ratios. Theupper curve illustrates risk of progression of monoclonal gammopathy of undeterminedsignificance in patients with an abnormal kappa/lambda free light chain ratio (1.65). The lower curve illustrates the risk of progression in patients with a normalratio.