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.
Laboratory Medicine, Immunology, University Hospitals Leuven, Katholieke Universiteit Leuven, Herestraat 49, 3000 Leuven, Belgium.
Pieter
P
Vermeersch
Martine
M
Vercammen
Annelies
A
Holvoet
Isabelle
I
Vande Broek
Isabelle Vande
IV
Broeck
Michel
M
Delforge
Xavier
X
Bossuyt
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