The predictive power of serum κ/λ ratios for discrimination between monoclonal gammopathy of undetermined significance and multiple myeloma

Enrique Bergón; Elena Miravalles; Elena Bergón; Isabel Miranda; Marta Bergón

doi:10.1515/CCLM.2005.004

Article

The predictive power of serum κ/λ ratios for discrimination between monoclonal gammopathy of undetermined significance and multiple myeloma

Enrique Bergón , Elena Miravalles , Elena Bergón , Isabel Miranda and Marta Bergón

Published/Copyright: September 21, 2011

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From the journal Clinical Chemistry and Laboratory Medicine (CCLM) Volume 43 Issue 1

Abstract

The predictive power of serum κ/λ ratios on initial presentation of immunoglobulin G (IgG) or IgA monoclonal component was studied to differentiate between monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) patients. The retrospective study involved 145 patients clinically diagnosed with monoclonal gammopathy of undetermined significance or multiple myeloma, who had serum M-protein IgG <35g/L or IgA <20g/L at M-protein detection. Serum light chains κ and λ were measured by fixed-time nephelometry. Test performance indices, predictive values and likelihood ratios were calculated according to the Weissler recommendation. MM patients were considered as diseased and MGUS patients as non-diseased in order to estimate the performance characteristics of serum κ/λ ratios. There was a statistically significant difference in κ/λ ratios distribution between both groups of patients, in both M-protein κ-type (Mann-Whitney U=168, p<0.001) and in M-protein λ-type (Mann-Whitney U=143, p<0.001). Negative likelihood ratios at threshold levels of 0.6 and 4.2 were 2.17- and 3.32-fold greater, respectively, than positive likelihood ratios, so that the predictive power of a serum κ/λ ratio within these limits is better in ruling out (negative predictive power) than ruling in disease (positive predictive power). The post-test characteristics of a serum κ/λ ratio interval between 0.6 and 4.2 in discriminating MGUS from MM in our geographic population were: sensitivity 0.96 (0.93–0.99 95%CI); specificity 0.70 (0.63–0.77); positive predictive value 0.68 (0.64–0.73); negative predictive value 0.96 (0.94–0.99); likelihood ratios (+)LR 3.23 (2.68–4.04); and (−)LR 17.16 (11.00–63.00). Thus, serum M-protein with a κ/λ ratio between 0.6 and 4.2 increases the posterior probability of MGUS from 0.60 to 0.96 in asymptomatic patients, for whom only monitoring may be suggested when the serum κ/λ ratio is within these limits.

Keywords: monoclonal gammopathy of undetermined significance (MGUS); multiple myeloma (MM); predictive power; serum κ/λ ratio

Corresponding author: Enrique Bergón, Department of Biochemistry, Hospital Universitario de Getafe, Cta. Toledo, Km 12,500, 28905 Getafe, Madrid, Spain Phone: +34-91-6839360, Fax: +34-91-6839748, enbergon@terra.es

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Received: 2004-6-1

Accepted: 2004-10-7

Published Online: 2011-9-21

Published in Print: 2005-1-1

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Articles in the same Issue

https://doi.org/10.1515/CCLM.2005.004

Keywords for this article

monoclonal gammopathy of undetermined significance (MGUS); multiple myeloma (MM); predictive power; serum κ/λ ratio