Use of interval-specific likelihood ratios improves clinical interpretation of serum FLC results for the diagnosis of malignant plasma cell disorders.
BACKGROUND
We examined whether the use of test result interval-specific likelihood ratios (LR) could improve the clinical interpretation of serum FLC kappa/lambda ratio for the diagnosis of malignant plasma cell disorders.


METHODS
We calculated LRs for different FLC kappa/lambda intervals using sera from patients diagnosed with intact multiple myeloma (MM), light chain MM (LCMM), non-secretory MM (NSMM) and light chain amyloidosis (AL-A). Consecutive patients with a clinical suspicion of a monoclonal B-cell disorder that were diagnosed with MGUS or no B-cell monoclonal disorder served as the disease control group.


RESULTS
Using LRs for different test result intervals, a distinction can be made between FLC kappa/lambda ratios that are within the normal diagnostic range, ratios that are inconclusive (1.66-5.0, LR+/-1), ratios that indicate the possible presence of a malignant plasma cell disorder (0.05-0.25 and >5.0-10, LR+/-10) and ratios that were suggestive of a malignant plasma cell disorder (<0.05 or >10; LR+/-50). A FLC kappa/lambda ratio within the normal diagnostic range virtually excluded LCMM and AL-A, but not intact MM or NSMM.


CONCLUSIONS
Interpreting serum FLC kappa/lambda ratios using LRs for different result intervals improves the clinical interpretation for the diagnosis of malignant plasma cell disorders excluding plasmacytoma.
Vermeersch
Pieter
P
Laboratory Medicine, Immunology, University Hospitals Leuven, Katholieke Universiteit Leuven, Herestraat 49, 3000 Leuven, Belgium.
Vercammen
Martine
M
Holvoet
Annelies
A
Vande Broek
Isabelle
I
Broeck
Isabelle Vande
IV
Delforge
Michel
M
Bossuyt
Xavier
X
D000686:Amyloidosis / Q000175:diagnosis; D016022:Case-Control Studies; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood*; D007145:Immunoglobulin kappa-Chains / Q000097:blood; D007146:Immunoglobulin lambda-Chains / Q000097:blood; D016013:Likelihood Functions; D009101:Multiple Myeloma / Q000175:diagnosis; D054219:Neoplasms, Plasma Cell / Q000175:diagnosis*; D011237:Predictive Value of Tests
D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains