Quantitation of free light chains in the cerebrospinal fluid reliably predicts their intrathecal synthesis.
BACKGROUND
The results of free light chains quantitation in the cerebrospinal fluid were recently compared with the presence of cerebrospinal fluid-restricted oligoclonal IgG, but not oligoclonal free kappa light chains and oligoclonal free lambda light chains. We therefore aimed to compare the performance of the quantitative tests with the qualitative one for the same molecule.


METHODS
Seventy-five paired cerebrospinal fluid and serum samples were analysed for oligoclonal IgG, oligoclonal free kappa light chains and oligoclonal free lambda light chains. Cerebrospinal fluid and serum free kappa and lambda light chains were quantified using Freelite™ kits on SPA Plus analyzer. ROC curves were analysed for the prediction of intrathecal synthesis and compared for cerebrospinal fluid concentration, cerebrospinal fluid/serum quotient (QfLC) and index (QfLC/QAlbumin). The presence of cerebrospinal fluid-restricted oligoclonal free kappa light chains and oligoclonal free lambda light chains bands was used as reference.


RESULTS
No statistically significant differences were observed among cerebrospinal fluid concentration, QfLC and index for the prediction of free light chain intrathecal synthesis. Each parameter was able to predict the occurrence of cerebrospinal fluid-restricted oligoclonal free light chain bands (AUCs 0.932-0.999). However, we noted elevated cerebrospinal fluid free light chain concentrations in the absence of cerebrospinal fluid-restricted oligoclonal free light chain bands in two patients with very high serum free light chain values.


CONCLUSIONS
Quantitation of cerebrospinal fluid free light chains reliably predicts their intrathecal synthesis. Yet, cerebrospinal fluid/serum quotient may still be preferred to correct for high serum free light chain concentrations. An appropriate formula should be sought to correct for blood-cerebrospinal fluid barrier status.
Department of Clinical Biochemistry, Institute of Laboratory Medicine, University Hospital Ostrava, Ostrava-Poruba, Czech Republic Clinic of Neurology, University Hospital Ostrava, Ostrava-Poruba, Czech Republic david.zeman@fno.cz.
David
D
Zeman
Department of Clinical Biochemistry, Institute of Laboratory Medicine, University Hospital Ostrava, Ostrava-Poruba, Czech Republic.
Pavlína
P
Kušnierová
Department of Clinical Biochemistry, Institute of Laboratory Medicine, University Hospital Ostrava, Ostrava-Poruba, Czech Republic.
Vladimír
V
Bartoš
Clinic of Neurology, University Hospital Ostrava, Ostrava-Poruba, Czech Republic.
Pavel
P
Hradílek
Clinic of Neurology, University Hospital Ostrava, Ostrava-Poruba, Czech Republic.
Barbora
B
Kurková
Clinic of Neurology, University Hospital Ostrava, Ostrava-Poruba, Czech Republic.
Olga
O
Zapletalová
D019963:Clinical Chemistry Tests / Q000379:methods*; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000096:biosynthesis* / Q000097:blood / Q000134:cerebrospinal fluid*; D007146:Immunoglobulin lambda-Chains / Q000096:biosynthesis* / Q000097:blood / Q000134:cerebrospinal fluid*; D013115:Spinal Canal / Q000378:metabolism
D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains
Cerebrospinal fluid; free light chains; oligoclonal IgG