Contributions
Abstract: P268
Type: Poster
Abstract Category: Clinical aspects of MS - Diagnosis and differential diagnosis
Background: Although cerebrospinal fluid (CSF) analysis is no longer necessary in the diagnostic work-up of multiple sclerosis (MS) evidence of intrathecal immunoglobulin G (IgG) production is highly supportive for the disease. Detection of CSF specific IgG oligoclonal bands (OCB) obtained with isoelectric focusing and subsequent immunoblotting still holds a status of the gold standard method, despite being technically demanding, enabling only qualitative IgG determination and subjective interpretation. Quantification of CSF kappa free light chains (KFLC), rather than intact immunoglobulin molecules, could represent an alternative easier to standardize method with comparable diagnostic accuracy.
Objective: In our study we aimed to compare diagnostic accuracy of our ultrasensitive OCB assay and intrathecal KFLC synthesis.
Methods: KFLC concentration was measured by nephelometry in paired serum and CSF samples of patients with MS (n = 80, 54 females) and non-inflammatory neurological diseases (n = 48, 26 females). KFLC indices and intrathecal KFLC fractions were calculated by previously defined formulae and used as main quantitative measures of intrathecal KFLC production. OCB assay consisted of agarose isoelectric focusing and IgG immunodetection by alkaline phosphatase-labelled anti-IgG antibody which was reported to be at least four times more sensitive than the standard peroxidase method.
Results: Diagnostic sensitivity of intrathecal KFLC synthesis was 97.4 % and 96.2 % for the KFLC index and intrathecal KFLC fraction respectively, compared to 90.0 % reached with the ultrasensitive OCB assay. Diagnostic specificity was 97.5 % for both intrathecal KFLC synthesis measures and 100 % for OCB. Importantly, 4 out of 7 OCB negative MS patients had elevated KFLC index when considering previously reported cut-off (≥ 5.9). CSF KFLC concentration alone was significantly higher in MS (median 1.7 mg/l, range 0.9 - 4.6 mg/l) than in comparison group (median 0.1 mg/l, range 0.1 - 0.2 mg/l; p < 0.0001) and similar was observed for the CSF KFLC to total protein ratio
(0.46 % vs. 0.03 %, p < 0.0001).
Conclusion: Our results further underline the relevance of KFLC as a diagnostic biomarker in MS. Intrathecal KFLC synthesis is the first quantitative measure that demonstrates comparable diagnostic accuracy as OCB while overcoming several drawbacks of OCB assays.
Disclosure:
Andreja Emersic: nothing to disclose
Vanesa Anadolli: nothing to disclose
Mladen Krsnik: nothing to disclose
Uros Rot received grants/research support from Biogen Idec and consultation fees/travel grants from Bayer, Biogen Idec, Genzyme, Merck-Serono, Novartis and Teva.
Support by the University Medical Centre Ljubljana research programme is acknowledged.
Abstract: P268
Type: Poster
Abstract Category: Clinical aspects of MS - Diagnosis and differential diagnosis
Background: Although cerebrospinal fluid (CSF) analysis is no longer necessary in the diagnostic work-up of multiple sclerosis (MS) evidence of intrathecal immunoglobulin G (IgG) production is highly supportive for the disease. Detection of CSF specific IgG oligoclonal bands (OCB) obtained with isoelectric focusing and subsequent immunoblotting still holds a status of the gold standard method, despite being technically demanding, enabling only qualitative IgG determination and subjective interpretation. Quantification of CSF kappa free light chains (KFLC), rather than intact immunoglobulin molecules, could represent an alternative easier to standardize method with comparable diagnostic accuracy.
Objective: In our study we aimed to compare diagnostic accuracy of our ultrasensitive OCB assay and intrathecal KFLC synthesis.
Methods: KFLC concentration was measured by nephelometry in paired serum and CSF samples of patients with MS (n = 80, 54 females) and non-inflammatory neurological diseases (n = 48, 26 females). KFLC indices and intrathecal KFLC fractions were calculated by previously defined formulae and used as main quantitative measures of intrathecal KFLC production. OCB assay consisted of agarose isoelectric focusing and IgG immunodetection by alkaline phosphatase-labelled anti-IgG antibody which was reported to be at least four times more sensitive than the standard peroxidase method.
Results: Diagnostic sensitivity of intrathecal KFLC synthesis was 97.4 % and 96.2 % for the KFLC index and intrathecal KFLC fraction respectively, compared to 90.0 % reached with the ultrasensitive OCB assay. Diagnostic specificity was 97.5 % for both intrathecal KFLC synthesis measures and 100 % for OCB. Importantly, 4 out of 7 OCB negative MS patients had elevated KFLC index when considering previously reported cut-off (≥ 5.9). CSF KFLC concentration alone was significantly higher in MS (median 1.7 mg/l, range 0.9 - 4.6 mg/l) than in comparison group (median 0.1 mg/l, range 0.1 - 0.2 mg/l; p < 0.0001) and similar was observed for the CSF KFLC to total protein ratio
(0.46 % vs. 0.03 %, p < 0.0001).
Conclusion: Our results further underline the relevance of KFLC as a diagnostic biomarker in MS. Intrathecal KFLC synthesis is the first quantitative measure that demonstrates comparable diagnostic accuracy as OCB while overcoming several drawbacks of OCB assays.
Disclosure:
Andreja Emersic: nothing to disclose
Vanesa Anadolli: nothing to disclose
Mladen Krsnik: nothing to disclose
Uros Rot received grants/research support from Biogen Idec and consultation fees/travel grants from Bayer, Biogen Idec, Genzyme, Merck-Serono, Novartis and Teva.
Support by the University Medical Centre Ljubljana research programme is acknowledged.