Assessment of Intrathecal Free Light Chain Synthesis: Comparison of Different Quantitative Methods with the Detection of Oligoclonal Free Light Chains by Isoelectric Focusing and Affinity-Mediated Immunoblotting

Abstract

ObjectivesWe aimed to compare various methods for free light chain (fLC) quantitation in cerebrospinal fluid (CSF) and serum and to determine whether quantitative CSF measurements could reliably predict intrathecal fLC synthesis. In addition, we wished to determine the relationship between free kappa and free lambda light chain concentrations in CSF and serum in various disease groups.MethodsWe analysed 166 paired CSF and serum samples by at least one of the following methods: turbidimetry (Freelite™, SPAPLUS), nephelometry (N Latex FLC™, BN ProSpec), and two different (commercially available and in-house developed) sandwich ELISAs. The results were compared with oligoclonal fLC detected by affinity-mediated immunoblotting after isoelectric focusing.ResultsAlthough the correlations between quantitative methods were good, both proportional and systematic differences were discerned. However, no major differences were observed in the prediction of positive oligoclonal fLC test. Surprisingly, CSF free kappa/free lambda light chain ratios were lower than those in serum in about 75% of samples with negative oligoclonal fLC test. In about a half of patients with multiple sclerosis and clinically isolated syndrome, profoundly increased free kappa/free lambda light chain ratios were found in the CSF.ConclusionsOur results show that using appropriate method-specific cut-offs, different methods of CSF fLC quantitation can be used for the prediction of intrathecal fLC synthesis. The reason for unexpectedly low free kappa/free lambda light chain ratios in normal CSFs remains to be elucidated. Whereas CSF free kappa light chain concentration is increased in most patients with multiple sclerosis and clinically isolated syndrome, CSF free lambda light chain values show large interindividual variability in these patients and should be investigated further for possible immunopathological and prognostic significance.

Free Kappa light chains in neuroinflammatory disorders: Complement rather than substitute?

“…A recently published report compared the performance of several κFLC quantification methods to κFLC IEF. They did not observe major differences regarding the diagnostic performances of the different techniques 29. No firm conclusion can be drawn from our results, due to the small number of samples analyzed by both techniques.…”

“…However, when omitting OCB status, a statistically significant difference was observed between the κFLC index of MS and INDC patients. They did not observe major differences regarding the diagnostic performances of the different techniques 29. 2 Specificity of intrathecal OCBs was also lower due to the inclusion of many patients with other inflammatory neurological disorders in our cohort, as reported byPetzold.…”

Kappa free light chains in cerebrospinal fluid to identify patients with oligoclonal bands

“…Determination of KFLC index (KFLC CSF:serum ratio divided by albumin CSF:serum ratio) has been introduced in the diagnosis of multiple sclerosis (MS) [7,8,[10][11][12][13]. Methodological differences in previously published studies hinder the transfer of previous study results into clinical routine [8,[10][11][12][13][14][15][16]. Furthermore, sparse data are available to assess the diagnostic accuracy of the KFLC index in predicting the presence of OCB independent of the underlying disease process.…”

Oligoclonal IgG and free light chains – comparison between agarose and polyacrylamide isoelectric focusing

“…Izoelektrická fokusace v agarózovém gelu pro průkaz o-fLC byla provedena na přístroji Multiphor II (GE Healthcare Life Sciences, Helsinky, Finsko) dříve popsaným postupem [7,8] Na PAG IEF/ IB byl jediný intratékálně syntezovaný IgG pás nalezen v 10 případech (9,4 %). Na IEF/ IF nebyl v šesti z těchto případů nalezen žádný pás, ve dvou případech byl nalezen rovněž jediný pás a v dalších dvou případech byly nalezeny dva, resp.…”

“…Tento test je používán vzácně vzhledem ke své větší pracnosti, zejména ve srovnání s novými automatizovanými kvantitativními metodami. U RS byla popsána také intratékální syntéza fLC typu lambda (free lambda light chains; fLLC) a přestože je nacházena vzácněji než intratékální syntéza IgG a fKLC [5, 7,8], recentní studie ukazují, že současná analýza fKLC a fLLC může mít prognostický význam [9][10][11].…”