The kappa free light chain index and oligoclonal bands have a similar role in the McDonald criteria

Laboratory Diagnosis of Intrathecal Synthesis of Immunoglobulins: A Review about the Contribution of OCBs and K-index

The diagnosis of MS relies on a combination of imaging, clinical examinations, and biological analyses, including blood and cerebrospinal fluid (CSF) assessments. G-Oligoclonal bands (OCBs) are considered a "gold standard" for MS diagnosis due to their high sensitivity and specificity. Recent advancements have involved the introduced of kappa free light chain (k-FLC) assay into cerebrospinal fluid (CSF) and serum (S), along with the albumin quotient, leading to the development of a novel biomarker known as the "K-index" or "k-FLC index". The use of the K-index has been recommended to decrease costs, increase laboratory efficiency, and to skip potential subjective operator-dependent risk that could happen during the identification of OCBs profiles. This review aims to provide a comprehensive overview and analysis of recent scientific articles, focusing on updated methods for MS diagnosis with an emphasis on the utility of the K-index. Numerous studies indicate that the K-index demonstrates high sensitivity and specificity, often comparable to or surpassing the diagnostic accuracy of OCBs evaluation. The integration of the measure of the K-index with OCBs assessment emerges as a more precise method for MS diagnosis. This combined approach not only enhances diagnostic accuracy, but also offers a more efficient and cost-effective alternative.

IgG and kappa free light chain CSF/serum indices: evaluating intrathecal immunoglobulin production in HIV infection in comparison with multiple sclerosis

OBJECTIVES

To study intrathecal kappa free light chain (KFLC) synthesis in people living with HIV (PLWH) in comparison with multiple sclerosis (MS).

METHODS

Cross-sectional analysis including 56 untreated and 150 well treated PLWH, and compared with 58 controls, and 223 MS patients.

RESULTS

Elevated serum/cerebrospinal fluid (CSF) IgG and KFLC indices were observed in untreated PLWH. Seventy percent of untreated PLWH had KFLC index above 6.1, a threshold associated with clinically isolated syndrome/MS diagnosis. No association was found between KFCL index and CSF markers of neuronal injury in either PLWH or MS patients.

CONCLUSIONS

HIV-related immune system dysfunction is often associated with an elevated KFLC index akin to those observed in MS. HIV infection should be considered as a differential diagnosis for patients presenting with neurological symptoms and increased intrathecal immunoglobulin synthesis.

Consensus recommendations for diagnosis and treatment of Multiple Sclerosis: 2023 revision of the MENACTRIMS guidelines

With evolving diagnostic criteria and the advent of new oral and parenteral therapies for Multiple Sclerosis (MS), most current diagnostic and treatment algorithms need revision and updating. The diagnosis of MS relies on incorporating clinical and paraclinical findings to prove dissemination in space and time and exclude alternative diseases that can explain the findings at hand. The differential diagnostic workup should be guided by clinical and laboratory red flags to avoid unnecessary tests. Appropriate selection of MS therapies is critical to maximize patient benefit. The current guidelines review the current diagnostic criteria for MS and the scientific evidence supporting treatment of acute relapses, radiologically isolated syndrome, clinically isolated syndrome, relapsing remitting MS, progressive MS, pediatric cases and pregnant women. The purpose of these guidelines is to provide practical recommendations and algorithms for the diagnosis and treatment of MS based on current scientific evidence and clinical experience.

Kappa Free Light Chain Index Predicts Disease Course in Clinically and Radiologically Isolated Syndromes

BACKGROUND AND OBJECTIVES

To evaluate whether the kappa free light chain index (K-index) can predict the occurrence of new T2-weighted MRI lesions (T2L) and clinical events in clinically isolated syndrome (CIS) and radiologically isolated syndrome (RIS).

METHODS

All consecutive patients presenting for the diagnostic workup, including CSF analysis, of clinical and/or MRI suspicion of multiple sclerosis (MS) since May 1, 2018, were evaluated. All patients diagnosed with CIS and RIS with at least 1-year follow-up were included. Clinical events and new T2L were collected during follow-up. The K-index performances in predicting new T2L and a clinical event were evaluated using time-dependent ROC analyses. The time to clinical event or new T2L was estimated using survival analysis according to the binarized K-index using an independent cutoff of 8.9, and the ability of each variable to predict outcomes was compared using the Harrell c-index.

RESULTS

One hundred and eighty two patients (146 CIS and 36 RIS, median age 39 [30; 48] y-o, 70% females) were included with a median follow-up of 21 [13, 33] months. One hundred five (58%) patients (85 CIS and 20 RIS) experienced new T2L, and 28 (15%; 21 CIS and 7 RIS) experienced a clinical event. The K-index could predict new T2L over time in CIS (area under the curve [AUC] ranging from 0.86 to 0.96) and in RIS (AUC ranging from 0.84 to 0.54) but also a clinical event in CIS (AUC ranging from 0.75 to 0.87). Compared with oligoclonal bands (OCBs), the K-index had a better sensitivity and a slight lower specificity in predicting new T2L and clinical events in both populations. In the predictive model, the K-index was the variable that best predict new T2L in both CIS and RIS but also clinical events in CIS (c-index ranging from 0.70 to 0.77), better than the other variables, including OCB.

DISCUSSION

This study provides evidence that the K-index predicts new T2L in CIS and RIS but also clinical attack in patients with CIS. We suggest adding the K-index in the further MS diagnosis criteria revisions as a dissemination-in-time biomarker.

Establishing the best combination of the kappa free light chain index and oligoclonal bands for an accurate diagnosis of multiple sclerosis

Introduction

The immunoglobulin kappa free light chain (KFLC) index has been proposed as a potentially suitable alternative to oligoclonal IgG bands (OCGB) for diagnosing multiple sclerosis (MS), offering automation and reduced processing time. However, there is no consensus on the preferred approach or how to combine both techniques.

Methods

This prospective cohort study aimed to determine the best utilization of OCGB and KFLC index in patients with a clinically isolated syndrome (CIS) followed for at least two years. OCGB and KFLC were assessed using isoelectric focusing and immunoblotting and turbidimetry, respectively. Sensitivity, specificity, and accuracy for diagnosing MS were calculated for each method.

Results

The study included 371 patients, with 260 (70.1 %) being women, and a median age of 34.9 (27.8 - 43.9) years. Using a cut-off value of 6.1, the KFLC index demonstrated a sensitivity and specificity of 86.3% and 93.9%, respectively. The sensitivity of OCGB (95.3%) was higher (p < 0.001 vs. KFLC index) and the specificity (100%) was comparable to that of the KFLC index (p = 0.5). The concordance between the methods was not uniform across all patients, with 97.8% agreement in patients with KFLC index ≥ 6.1 and 56.0 % in patients with KFLC index < 6.1. In patients with a KFLC index < 6.1, OCGB still identified 75.0 % of MS patients due to its higher sensitivity. An algorithm using the KFLC index as a screening tool and OCGB as an alternative for patients with a negative KFLC index result achieved an accuracy of 96.3 %.

Discussion

Combining the KFLC index and OCGB can provide an easily reproducible and accurate method for diagnosing MS, with OCGB primarily reserved for patients with a KFLC index < 6.1.

Kappa free light chains index in multiple sclerosis very long-term prognosis

Introduction

The role of the kappa-free light chain (kFLC) in the diagnosis of multiple sclerosis (MS) and, to a lesser extent, its role as a medium-term prognostic marker have been extensively studied. This study aimed to explore its potential as a long-term prognostic marker for MS.

Methods

We performed an exploratory retrospective observational study by selecting patients systemically followed up in our MS unit with available cerebrospinal fluid and serum samples at the time of initial evaluation. Two groups were defined: benign MS (bMS), defined as patients with Expanded Disability Status Scale (EDSS) ≤ 3 at 10 years of follow-up, and aggressive MS (aMS), defined as patients with EDSS ≥ 6 at 15 years of follow-up. Clinical variables were collected, and the immunoglobulin G (IgG) index, kFLC index, and oligoclonal bands (OCB) were determined for all patients and compared between the groups.

Results

Twenty bMS and 15 aMS patients were included in this study. Sixty percent (21/35) were female, and the mean age at the time of the first symptom was 31.5 ± 9.45 years, with no statistical differences between groups. Median follow-up time was 19.8 years (Interquartile range, IQR 15.9-24.6). The median EDSS scores at the last follow-up were 1.5 and 7.5 in the bMS and the aMS group, respectively. No statistically significant differences were found in the kFLC index between the two groups (136.6 vs. 140.27, p=0.59). The IgG index was positive in 62.9% of patients (55% bMS vs. 73.3% aMS, p>0.05), and OCB was positive in 88.6% (90% bMS vs. 86.7% aMS, p>0.05). A significant positive correlation was found between IgG and kFLC indices (rs = 0.85, p<0.001).

Conclusion

Given the absence of differences between the two groups with opposite disease courses, it is unlikely that the kFLC index is a reliable and powerful marker of long-term prognosis in MS.

Intrathecal kappa free light chain synthesis is associated with worse prognosis in relapsing-remitting multiple sclerosis

BACKGROUND

While kappa free light chain (KFLC) index has become a useful diagnostic biomarker in multiple sclerosis (MS), its prognostic properties are less explored. B cells play a crucial role in MS pathogenesis, but the impact from increased intrathecal production of immunoglobulins and KFLC remains to be determined. Recently, it has become evident that insidious worsening is not confined to progressive MS but is also common in relapsing-remitting MS (RRMS), a feature known as progression independent of relapse activity (PIRA).

METHODS

We retrospectively identified 131 patients with clinically isolated syndrome or early RRMS who had determined KFLC index as part of their diagnostic workup. Demographic and clinical data were extracted from the Swedish MS registry. Associations of baseline KFLC index with evidence of disease activity (EDA) and PIRA were investigated in multivariable cox proportional hazards regression models.

RESULTS

KFLC index was significantly higher in PIRA (median 148.5, interquartile range [IQR] 106.9-253.5) compared with non-PIRA (78.26, IQR 28.93-186.5, p = 0.009). In a multivariable cox regression model adjusted for confounders, KFLC index emerged as an independent risk factor for PIRA (adjusted hazard ratio [aHR] 1.005, 95% confidence interval [CI] 1.002-1.008, p = 0.002). Dichotomized by the cut-off value KFLC index > 100, patients with KFLC index > 100 had an almost fourfold increase in the risk for developing PIRA. KFLC index was also predictive of evidence of disease activity during follow-up.

CONCLUSIONS

Our data indicate that high KFLC index at baseline is predictive of PIRA, EDA-3, and overall worse prognosis in MS.

Myelin Oligodendrocyte Glycoprotein Antibodies in Adults with a First Demyelinating Event Suggestive of Multiple Sclerosis

OBJECTIVE

Myelin oligodendrocyte glycoprotein antibodies (MOG-Ab) distinguish multiple sclerosis (MS) from MOG-associated disease in most cases. However, studies analyzing MOG-Ab at the time of a first demyelinating event suggestive of MS in adults are lacking. We aimed to (1) evaluate the prevalence of MOG-Ab in a first demyelinating event suggestive of MS and (2) compare clinical and paraclinical features between seropositive (MOG-Ab+) and seronegative (MOG-Ab-) patients.

METHODS

Six hundred thirty adult patients with available serum samples obtained within 6 months from the first event were included. MOG-Ab were analyzed using a live cell-based assay. Statistical analyses included parametric and nonparametric tests, logistic regression, and survival models.

RESULTS

MOG-Ab were positive in 17 of 630 (2.7%). Fourteen out of 17 (82.4%) MOG-Ab+ patients presented with optic neuritis (ON) compared to 227of 613 (37.0%) MOG-Ab- patients (p = 0.009). Cerebrospinal fluid-restricted oligoclonal bands (CSF-OBs) were found in 2 of 16 (12.5%) MOG-Ab+ versus 371 of 601 (61.7%) MOG-Ab- subjects (p < 0.001). Baseline brain magnetic resonance imaging (MRI) was normal in 9 of 17 (52.9%) MOG-Ab+ versus 153 of 585 (26.2%) MOG-Ab- patients (p = 0.029). Absence of CSF-OBs and ON at onset were independently associated with MOG-Ab positivity (odds ratio [OR] = 9.03, 95% confidence interval [CI] = 2.04-53.6, p = 0.009; and OR = 4.17, 95% CI = 1.15-19.8, p = 0.042, respectively). Of MOG-Ab+ patients, 22.9% (95% CI = 0.0-42.7) compared to 67.6% (95% CI = 63.3-71.3) of MOG-Ab- patients fulfilled McDonald 2017 criteria at 5 years (log-rank p = 0.003).

INTERPRETATION

MOG-Ab are infrequent in adults with a first demyelinating event suggestive of MS. However, based on our results, we suggest to determine these antibodies in those patients with ON and absence of CSF-OBs, as long as the brain MRI is not suggestive of MS. ANN NEUROL 2023.

Differential diagnosis of suspected multiple sclerosis: an updated consensus approach

Accurate diagnosis of multiple sclerosis requires careful attention to its differential diagnosis-many disorders can mimic the clinical manifestations and paraclinical findings of this disease. A collaborative effort, organised by The International Advisory Committee on Clinical Trials in Multiple Sclerosis in 2008, provided diagnostic approaches to multiple sclerosis and identified clinical and paraclinical findings (so-called red flags) suggestive of alternative diagnoses. Since then, knowledge of disorders in the differential diagnosis of multiple sclerosis has expanded substantially. For example, CNS inflammatory disorders that present with syndromes overlapping with multiple sclerosis can increasingly be distinguished from multiple sclerosis with the aid of specific clinical, MRI, and laboratory findings; studies of people misdiagnosed with multiple sclerosis have also provided insights into clinical presentations for which extra caution is warranted. Considering these data, an update to the recommended diagnostic approaches to common clinical presentations and key clinical and paraclinical red flags is warranted to inform the contemporary clinical evaluation of patients with suspected multiple sclerosis.

Kappa free light chain and neurofilament light independently predict early multiple sclerosis disease activity-a cohort study

BACKGROUND

Inter-individual courses of multiple sclerosis (MS) are extremely variable. The objective of this study was to investigate whether κ-free light chain (κ-FLC) index and serum neurofilament light (sNfL) have an additive predictive value for MS disease activity.

METHODS

Patients with early MS who had cerebrospinal fluid (CSF) and serum sampling at disease onset were followed for four years. At baseline, age, sex, disease duration, number of T2-hyperintense (T2L), and contrast-enhancing T1 lesions (CEL) on MRI were determined. During follow-up, the occurrence of a second clinical attack and start of disease-modifying treatment (DMT) were registered. κ-FLC was measured by nephelometry, and κ-FLC index calculated as [CSF κ-FLC/serum κ-FLC]/albumin quotient. sNfL was determined by single-molecule array, and age- and body-mass-index adjusted Z scores were calculated.

FINDINGS

A total of 86 patients at a mean age of 33 ± 10 years and with a female predominance of 67% were included; 36 (42%) patients experienced a second clinical attack during follow-up. Cox regression analysis adjusted for age, sex, T2L, CEL, disease and follow-up duration, and DMT use during follow-up revealed that both κ-FLC index as well as sNfL Z score independently predict time to second clinical attack. The chance for freedom of relapse within 12 months was 2% in patients with high levels of κ-FLC index (>100) and high sNfL Z score (>3), 30% in patients with high κ-FLC index (>100) and lower sNfL Z score (≤3), 70% in patients with lower κ-FLC index (≤100) but high sNfL Z score (>3), and 90% in patients with lower levels of κ-FLC index (≤100) and sNfL Z score (≤3).

INTERPRETATION

κ-FLC index and sNfL Z score have an additive predictive value for early MS disease activity that is independent of known predictors.

FUNDING

This study was funded by a grant of the charitable foundation of the Austrian Multiple Sclerosis Society.

Cerebrospinal fluid kappa free light chains for the diagnosis of multiple sclerosis: A consensus statement

Cerebrospinal fluid (CSF) analysis is of utmost importance for diagnosis and differential diagnosis of patients with suspected multiple sclerosis (MS). Evidence of intrathecal immunoglobulin G (IgG) synthesis proves the inflammatory nature of the disease, increases diagnostic certainty and substitutes for dissemination in time according to current diagnostic criteria. The gold standard to determine intrathecal IgG synthesis is the detection of CSF-restricted oligoclonal bands (OCBs). However, advances in laboratory methods brought up κ-free light chains (FLCs) as a new biomarker, which are produced in excess over intact immunoglobulins and accumulate in CSF in the case of central nervous system-derived inflammation. Overwhelming evidence showed a high diagnostic accuracy of intrathecal κ-FLC synthesis in MS with sensitivity and specificity of approximately 90% similar to OCB. κ-FLCs have advantages as its detection is fast, easy, cost-effective, reliable, rater-independent and returning quantitative results which might also improve the value of predicting MS disease activity. An international panel of experts in MS and CSF diagnostics developed a consensus of all participants. Six recommendations are given for establishing standard CSF evaluation in patients suspected of having MS. The panel recommended to include intrathecal κ-FLC synthesis in the next revision of MS diagnostic criteria as an additional tool to measure intrathecal immunoglobulin synthesis.

High levels of kappa free light chain synthesis predict cognitive decline in relapsing-remitting multiple sclerosis

Background

Evolving evidence suggests that measurement of cerebrospinal fluid (CSF) kappa free light chain (KFLC) synthesis has high diagnostic sensitivity and specificity for multiple sclerosis (MS), but its prognostic ability is less investigated. The usefulness of KFLC in predicting cognitive impairment (CI) is still unknown.

Methods

In a monocentric longitudinal retrospecitve cohort study, KFLC-index ([CSF KFLC/serum KFLC]/[CSF albumin/serum albumin]) measured by latex-enhanced immunonephelometry was prospectively determined as part of the diagnostic workup in patients with early relapsing-remitting MS (RRMS, n=77). The ability of KFLC-index to predict information processing speed (IPS) worsening as assessed with the symbol digit modalities test (SDMT) was investigated in univariable and multivariable models.

Results

In patients with KFLC-index>100 (n=31), 11 subjects (35.5%) showed reduced SDMT scores by ≥8 points at follow-up (mean follow-up time 7.3 ± 2.6 years), compared with their baseline scores (p=0.01). Baseline KFLC-index>100 was strongly associated with a higher hazard of SDMT score reduction at follow-up (adjusted hazard ratio 10.5, 95% confidence interval 2.2-50.8, p=0.003; median time to SDMT reduction 7 years).

Conclusion

Intrathecal KFLC synthesis has become an attractive diagnostic tool for MS. We show for the first time that in a real-world setting of early RRMS, KFLC-index predicted cognitive decline. Whether this predictive ability of KFLC-index also concerns other cognitive domains than IPS, warrants further investigations.

Kappa Free Light Chain Biomarkers Are Efficient for the Diagnosis of Multiple Sclerosis

Background and Objectives

Kappa free light chains (KFLC) seem to efficiently diagnose MS. However, extensive cohort studies are lacking to establish consensus cut-offs, notably to rule out non-MS autoimmune CNS disorders. Our objectives were to (1) determine diagnostic performances of CSF KFLC, KFLC index, and KFLC intrathecal fraction (IF) threshold values that allow us to separate MS from different CNS disorder control populations and compare them with oligoclonal bands' (OCB) performances and (2) to identify independent factors associated with KFLC quantification in MS.

Methods

We conducted a retrospective multicenter study involving 13 French MS centers. Patients were included if they had a noninfectious and nontumoral CNS disorder, eligible data concerning CSF and serum KFLC, albumin, and OCB. Patients were classified into 4 groups according to their diagnosis: MS, clinically isolated syndrome (CIS), other inflammatory CNS disorders (OIND), and noninflammatory CNS disorder controls (NINDC).

Results

One thousand six hundred twenty-one patients were analyzed (675 MS, 90 CIS, 297 OIND, and 559 NINDC). KFLC index and KFLC IF had similar performances in diagnosing MS from nonselected controls and OIND (p= 0.123 andp= 0.991 for area under the curve [AUC] comparisons) and performed better than CSF KFLC (p< 0.001 for all AUC comparisons). A KFLC index of 8.92 best separated MS/CIS from the entire nonselected control population, with better performances than OCB (p< 0.001 for AUC comparison). A KFLC index of 11.56 best separated MS from OIND, with similar performances than OCB (p= 0.065). In the multivariate analysis model, female gender (p= 0.003), young age (p= 0.013), and evidence of disease activity (p< 0.001) were independent factors associated with high KFLC index values in patients with MS, whereas MS phenotype, immune-modifying treatment use at sampling, and the FLC analyzer type did not influence KFLC index.

Discussion

KFLC biomarkers are efficient tools to separate patients with MS from controls, even when compared with other patients with CNS autoimmune disorder. Given these results, we suggest using KFLC index or KFLC IF as a criterion to diagnose MS.

Classification of Evidence

This study provides Class III evidence that KFLC index or IF can be used to differentiate patients with MS from nonselected controls and from patients with other autoimmune CNS disorders.

The Use of Kappa Free Light Chains to Diagnose Multiple Sclerosis

Background: The positive implications of using free light chains in diagnosing multiple sclerosis have increasingly gained considerable interest in medical research and the scientific community. It is often presumed that free light chains, particularly kappa and lambda free light chains, are of practical use and are associated with a higher probability of obtaining positive results compared to oligoclonal bands. The primary purpose of the current paper was to conduct a systematic review to assess the up-to-date methods for diagnosing multiple sclerosis using kappa and lambda free light chains. Method: An organized literature search was performed across four electronic sources, including Google Scholar, Web of Science, Embase, and MEDLINE. The sources analyzed in this systematic review and meta-analysis comprise randomized clinical trials, prospective cohort studies, retrospective studies, controlled clinical trials, and systematic reviews. Results: The review contains 116 reports that includes 1204 participants. The final selection includes a vast array of preexisting literature concerning the study topic: 35 randomized clinical trials, 21 prospective cohort studies, 19 retrospective studies, 22 controlled clinical trials, and 13 systematic reviews. Discussion: The incorporated literature sources provided integral insights into the benefits of free light chain diagnostics for multiple sclerosis. It was also evident that the use of free light chains in the diagnosis of clinically isolated syndrome (CIS) and multiple sclerosis is relatively fast and inexpensive in comparison to other conventional state-of-the-art diagnostic methods, e.g., using oligoclonal bands (OCBs).