High sensitivity of free lambda and free kappa light chains for detection of intrathecal immunoglobulin synthesis in cerebrospinal fluid

So far, an inflammation of the central nervous system (CNS) is diagnosed by immunoglobulin measurement in cerebrospinal fluid (CSF) and serum as well as by determination of the oligoclonal bands. With the free kappa and lambda light chains, new markers to diagnose intrathecal synthesis are available. In addition to routine diagnostic tests and the assessment of standard parameters, free immunoglobulin light chains were measured in the CSF of patients with neurological disorders. A significant agreement was found between an increase in free kappa light chain CSF serum quotients and results of the currently widely applied method of oligoclonal band measurement for the detection of intrathecal immunoglobulin synthesis. A sensitivity of 95% and 100% specificity for free kappa light chain concentrations at a cut-off of 0.41 mg/l was determined for free kappa light chains compared with oligoclonal bands. However, the free lambda light chains in 20 out of the 110 investigated samples were characterized by inconsistent behaviour. These otherwise unremarkable samples yielded increased CSF quotients, leading to the assumption that free lambda light chains represent a highly sensitive measure of intrathecal immunologlobulin synthesis. Thirteen of the 20 samples described above were obtained from patients with cerebral infarction, 4 samples derived from patients with cerebral paresis (primarily facial paresis), one sample was from a patient with multisystem atrophy and two were obtained from patients with migraine and neuralgia. These findings suggest that the high sensitivity of lambda light chains for the detection intrathecal immunoglobulin synthesis may be of benefit in establishing clinical diagnoses.