Evaluation of the N Latex free light chain assay in the diagnosis and monitoring of AL amyloidosis

Mollee, Peter, Tate, Jill and Pretorius, Carel J. (2013) Evaluation of the N Latex free light chain assay in the diagnosis and monitoring of AL amyloidosis. Clinical Chemistry and Laboratory Medicine, 51 12: 2303-2310. doi:10.1515/cclm-2013-0361

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Author Mollee, Peter
Tate, Jill
Pretorius, Carel J.
Title Evaluation of the N Latex free light chain assay in the diagnosis and monitoring of AL amyloidosis
Journal name Clinical Chemistry and Laboratory Medicine   Check publisher's open access policy
ISSN 1434-6621
Publication date 2013-12-01
Year available 2013
Sub-type Article (original research)
DOI 10.1515/cclm-2013-0361
Open Access Status File (Publisher version)
Volume 51
Issue 12
Start page 2303
End page 2310
Total pages 8
Place of publication Berlin, Germany
Publisher Walter de Gruyter GmbH
Language eng
Formatted abstract
Background: We compared a novel assay for free light chain (FLC) quantitation based on monoclonal antibodies (N-Latex, Siemens, Germany) to the established polyclonal antibody-based assay (Freelite™, The Binding Site, UK) in AL amyloidosis.

Methods: Sixty-two diagnostic samples were analysed on a BNII nephelometer, 32 of which also had a post-treatment sample.

Results: In the diagnostic samples: for AL of κ type, the median involved FLC (iFLC) was significantly lower by the N-Latex assay (289 vs. 667 mg/L, p=0.0002) whereas for λ AL the values were similar (148 vs. 161 mg/L, p=0.84). Measurable disease, defined as a difference between involved and uninvolved FLC (dFLC) >50 mg/L was present in 82% by the N-Latex assay compared to 89% by the Freelite™ assay. For diagnostic sensitivity, the FLC ratio was normal in 21% (95% CI 12%-33%) and 15% (95% CI 7%-26%) of patients by the N-Latex and Freelite™ assays, respectively. The combination of serum and urine immunofixation electrophoresis with either FLC assay allowed identification of the amyloidogenic clone in 98% producing comparable sensitivity. For the monitoring samples the median reduction in dFLC was 68% for the N-Latex assay and 77% for the Freelite ™ assay (p=0.04). This led to some differences in assigning response categories. Partial response as assigned by both assays predicted overall survival (N-Latex p=0.0015, Freelite™ p=0.022).

Conclusions: There are differences between FLC as measured by the N-Latex and Freelite™ assays, but overall the two assays have similar diagnostic sensitivity. Disease response calculated by both assays predicts survival but more clinical validation is required.
Keyword AL amyloidosis
Free light chain assay
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2014 Collection
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