The diagnostic value of IgG index versus oligoclonal bands in cerebrospinal fluid of patients with multiple sclerosis

Body fluid markers for multiple sclerosis and differential diagnosis from atypical demyelinating disorders

INTRODUCTION

Body fluid markers could be helpful to predict the conversion into clinically definite multiple sclerosis (MS) in people with a first demyelinating event of the central nervous system (CNS). Consequently, biomarkers such as oligoclonal bands, which are integrated in the current MS diagnostic criteria, could assist early MS diagnosis.

AREAS COVERED

This review examines existing knowledge on a broad spectrum of body fluid markers in people with a first CNS demyelinating event, explores their potential to predict conversion to MS, to assess MS disease activity, as well as their utility to differentiate MS from atypical demyelinating disorders such as neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein associated disease.

EXPERT OPINION

This field of research has shown a dramatic increase of evidence, especially in the last decade. Some biomarkers are already established in clinical routine (e.g. oligoclonal bands) while others are currently implemented (e.g. kappa free light chains) or considered as breakthroughs (e.g. neurofilament light). Determination of biomarkers poses challenges for continuous monitoring, especially if exclusively detectable in cerebrospinal fluid. A handful of biomarkers are measurable in blood which holds a significant potential.

Insights into the interplay between Epstein-Barr virus (EBV) and multiple sclerosis (MS): A state-of-the-art review and implications for vaccine development

Background and Aims

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS). MS results from an inflammatory process leading to the loss of neural tissue and increased disability over time. The role of Epstein Barr Virus (EBV), as one of the most common global viruses, in MS development has been the subject of several studies. However, many related questions are still unanswered. This study aimed to review the connection between MS and EBV and provide a quick outline of MS prevention using EBV vaccination.

Methods

For this narrative review, an extensive literature search using specific terms was conducted across online databases, including PubMed/Medline, Scopus, Web of Science, and Google Scholar, to identify pertinent studies.

Results

Several studies proved that almost 100% of people with MS showed a history of EBV infection, and there was an association between high titers of EBV antibodies and an increased risk of MS development. Various hypotheses are proposed for how EBV may contribute to MS directly and indirectly: (1) Molecular Mimicry, (2) Mistaken Self, (3) Bystander Damage, and (4) Autoreactive B cells infected with EBV.

Conclusion

Given the infectious nature of EBV and its ability to elude the immune system, EBV emerges as a strong candidate for being the underlying cause of MS. The development of an EBV vaccine holds promise for preventing MS; however, overcoming the challenge of creating a safe and efficacious vaccine presents a significant obstacle.

The elusive nature of the oligoclonal bands in multiple sclerosis

Intrathecal immunoglobulin G (IgG) and oligoclonal bands (OCBs) detected in both the brain and cerebrospinal fluid (CSF) are seminal features of multiple sclerosis (MS). The presence of OCBs correlates with elevated disease burden and severity and supports the diagnosis of MS. Despite numerous investigations into the potential viral and autoantigen targets, the precise antigenic specificity of OCBs has remained elusive. We have little knowledge of the nature regarding these oligoclonal IgG bands. Here, we present compelling evidence highlighting the key findings that both OCBs and intrathecal IgG antibodies are under genetic control and that OCBs originate from clonal B-cells in both the periphery and CNS. We propose that MS OCBs are IgG immune complexes composed of IgG1 and IgG3 antibodies and that the pathological role of OCB stems from the IgG effector functions of these complexes, leading to demyelination and axonal injuries. We present additional evidence regarding the nature of MS OCBs: (1) disease-modifying therapies have been shown to affect CSF OCB; (2) OCBs have also been detected in several neuroinfectious diseases; (3) Epstein-Barr virus (EBV) has been particularly linked with MS pathogenesis, and its association with OCB is an important area of study. Although OCBs are closely associated with MS, more meticulously planned research is necessary to clarify the precise role of OCB in MS, both in terms of disease pathogenesis and diagnosis.

The diagnosis of multiple sclerosis: what has changed in diagnostic criteria?

Multiple sclerosis (MS) is a chronic, demyelinating disease affecting the central nervous system. Diagnosis of MS is based on the proof of disease dissemination in time (DIT) and dissemination in space (DIS) and excluding other disorders that can mimic multiple sclerosis in laboratory tests and clinical manifestation. Over the years the diagnostic criteria have evolved; the introduction of magnetic resonance in the McDonald's 2001 criteria was revolutionary. Since then, the criteria have been modified up to the currently used McDonald 2017. The aim of this review is to analyse the 2017 McDonald criteria, assess what has changed from the 2010 criteria, and present the impact of revised criteria on rapid and accurate diagnosis of MS. The main differences are as follows: inclusion of oligoclonal bands in cerebrospinal fluid as a DIT criterion, and symptomatic and cortical lesions in magnetic resonance imaging are counted in the determination of DIS and DIT. We present also the newest recommendations of the Polish Medical Society of Radiology and the Polish Society of Neurology and international group of North American Imaging in Multiple Sclerosis and Consortium of Multiple Sclerosis Centers, as well as future directions for further investigations. A proper diagnosis is crucial for the patient's quality of life, to give the possibility of early treatment, and to help avoid misdiagnosis and unnecessary therapy.

A dynamic interpretation of κFLC index for the diagnosis of multiple sclerosis: a change of perspective

BACKGROUND

Previous studies attempted to define the best threshold for κ free light chains (κFLC) index, confirming higher sensitivity (Se) but less specificity (Sp) compared with IgG oligoclonal bands (OCB) for the diagnosis of MS.

OBJECTIVE

To evaluate the diagnostic accuracy of different κFLC index intervals in a miscellaneous cohort of neurological patients, proposing a procedural flowchart for MS diagnosis.

METHODS

We analyzed data from 607 patients diagnosed with MS (179), CIS (116), other inflammatory (94) or non-inflammatory neurological diseases (218). Measures of diagnostic accuracy were reported for different potential thresholds of κFLC index, and for IgG OCB and IgG index. Binary logistic regression was to used to calculate the odds of being diagnosed with MS based on each increase of κFLC index.

RESULTS

CSF IgG OCB showed 72.2% Se (CI 95% 68.4-75.7) and 95.2% Sp (CI 95% 93.1-96.7) in discriminating between MS/CIS and controls, with an AUC of 0.84 (CI 95% 0.80-0.87). The highest diagnostic accuracy was reported for κFLC index cut-off of 5.0 (Se = 85.4%, Sp = 90.4%, AUC = 0.88), while a threshold of 11.0 exhibited higher Sp (95.5%, 95% CI 93.1-97.1) than IgG OCB. AUCs for all thresholds between 4.25 and 6.6 were not significantly different from each other, but were significantly higher than the AUC of IgG OCB (p < 0.05). The odds of being diagnosed with MS/CIS increased by 17.1% for each unit increase of κFLC index (OR = 1.17; 95% CI 1.12-1.23; p < 0.001).

CONCLUSION

κFLC index performed better than CSF IgG OCB in supporting the diagnosis of MS/CIS, with the advantage of being a cost-effective and quantitative analysis.

Cerebrospinal fluid oligoclonal bands in Chinese patients with multiple sclerosis: the prevalence and its association with clinical features

Background

Cerebrospinal fluid oligoclonal band (CSF-OCB) is an established biomarker in diagnosing multiple sclerosis (MS), however, there are no nationwide data on CSF-OCB prevalence and its diagnostic performance in Chinese MS patients, especially in the virtue of common standard operation procedure (SOP).

Methods

With a consensus SOP and the same isoelectric focusing system, we conducted a nationwide multi-center study on OCB status in consecutively, and recruited 483 MS patients and 880 non-MS patients, including neuro-inflammatory diseases (NID, n = 595) and non-inflammatory neurological diseases (NIND, n=285). Using a standardized case report form (CRF) to collect the clinical, radiological, immunological, and CSF data, we explored the association of CSF-OCB positivity with patient characters and the diagnostic performance of CSF-OCB in Chinese MS patients. Prospective source data collection, and retrospective data acquisition and statistical data analysis were used.

Findings

369 (76.4%) MS patients were OCB-positive, while 109 NID patients (18.3%) and 6 NIND patients (2.1%) were OCB-positive, respectively. Time from symptom onset to diagnosis was significantly shorter in OCB-positive than that in OCB-negative MS patients (13.2 vs 23.7 months, P=0.020). The prevalence of CSF-OCB in Chinese MS patients was significantly higher in high-latitude regions (41°-50°N)(P=0.016), and at high altitudes (>1000m)(P=0.025). The diagnostic performance of CSF-OCB differentiating MS from non-MS patients yielded a sensitivity of 76%, a specificity of 87%.

Interpretation

The nationwide prevalence of CSF-OCB was 76.4% in Chinese MS patients, and demonstrated a good diagnostic performance in differentiating MS from other CNS diseases. The CSF-OCB prevalence showed a correlation with high latitude and altitude in Chinese MS patients.

The diagnostic utility of IgG index and oligoclonal bands for multiple sclerosis in a neurology hospital patient population

BACKGROUND

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. Diagnosis is based on the 2017 revised McDonald criteria. Unmatched oligoclonal bands (OCB) within the CSF (i.e. positive OCB) can substitute for dissemination in time by magnetic resonance imaging (MRI). Simonsen et al. (2020) claimed a raised (>0.7) immunoglobulin G (IgG) index could replace OCB status. This study aimed to establish the diagnostic utility of IgG index for MS in the population served by The Walton Centre NHS Foundation Trust (WCFT) a neurology and neurosurgery hospital, and to derive a population-based IgG index reference interval.

METHODS

OCB results from the laboratory information system (LIS) were collated from November 2018 to 2021. Final diagnosis and medication history was obtained from the electronic patient record. Exclusions were made based on age (<18 years) at the time of lumbar puncture (LP) disease-modifying treatment prior to LP, unknown IgG index and unclear OCB patterns.

RESULTS

935 of 1101 results remained following exclusions. 226 (24.2%) had a diagnosis of MS, 212 (93.8%) were OCB positive and 165 (73.0%) had a raised IgG index. The diagnostic specificity of a raised IgG index was calculated at 90.3% compared to 86.9% for positive OCB. 386 results with negative OCB were used to establish the IgG index reference interval (0.36-0.68) at 95th percentiles.

CONCLUSION

This study provides evidence that IgG index should not replace OCB in the diagnosis of MS. >0.7 is an appropriate cut-off to define a raised IgG index for the patient population.

Clinical associations and characteristics of the polyspecific intrathecal immune response in elderly patients with non-multiple sclerosis chronic autoimmune-inflammatory neurological diseases - a retrospective cross-sectional study

Introduction

The polyspecific intrathecal immune response (PSIIR), aka MRZ reaction (M = measles, R = rubella, Z = zoster, optionally Herpes simplex virus, HSV) is defined as intrathecal immunoglobulin synthesis (IIS) for two or more unrelated viruses. Although an established cerebrospinal fluid (CSF) biomarker for multiple sclerosis (MS), a chronic autoimmune-inflammatory neurological disease (CAIND) of the central nervous system (CNS) usually starting in young adulthood, the full spectrum of CAINDs with a positive PSIIR remains ill defined.

Methods

In this retrospective, cross-sectional study, patients with CSF-positive oligoclonal bands (OCB) and - to enrich for non-MS diagnoses - aged ≥50 years were enrolled.

Results

Of 415 with PSIIR testing results (MRZ, HSV optional), 76 were PSIIR-positive. Of these, 25 (33%) did not meet the diagnostic criteria for MS spectrum diseases (MS-S) comprising clinically or radiologically isolated syndrome (CIS/RIS) or MS. PSIIR-positive non-MS-S phenotypes were heterogenous with CNS, peripheral nerve and motor neuron involvement and often defied unequivocal diagnostic classification. A rating by neuroimmunology experts suggested non-MS CAINDs in 16/25 (64%). Long-term follow-up available in 13 always showed a chronically progressive course. Four of five responded to immunotherapy. Compared to MS-S patients, non-MS CAIND patients showed less frequent CNS regions with demyelination (25% vs. 75%) and quantitative IgG IIS (31% vs. 81%). MRZ-specific IIS did not differ between both groups, while additional HSV-specific IIS was characteristic for non-MS CAIND patients.

Discussion

In conclusion, PSIIR positivity occurs frequently in non-MS-S patients ≥50 years. Although sometimes apparently coincidental, the PSIIR seems to represent a suitable biomarker for previously unnoticed chronic neurologic autoimmunities, which require further characterization.

Immune profiling in multiple sclerosis: a single-center study of 65 cytokines, chemokines, and related molecules in cerebrospinal fluid and serum

Introduction

The understanding of the pathophysiology of multiple sclerosis (MS) has evolved alongside the characterization of cytokines and chemokines in cerebrospinal fluid (CSF) and serum. However, the complex interplay of pro- and anti-inflammatory cytokines and chemokines in different body fluids in people with MS (pwMS) and their association with disease progression is still not well understood and needs further investigation. Therefore, the aim of this study was to profile a total of 65 cytokines, chemokines, and related molecules in paired serum and CSF samples of pwMS at disease onset.

Methods

Multiplex bead-based assays were performed and baseline routine laboratory diagnostics, magnetic resonance imaging (MRI), and clinical characteristics were assessed. Of 44 participants included, 40 had a relapsing-remitting disease course and four a primary progressive MS.

Results

There were 29 cytokines and chemokines that were significantly higher in CSF and 15 in serum. Statistically significant associations with moderate effect sizes were found for 34 of 65 analytes with sex, age, CSF, and MRI parameters and disease progression.

Discussion

In conclusion, this study provides data on the distribution of 65 different cytokines, chemokines, and related molecules in CSF and serum in newly diagnosed pwMS.

The Immune System and Depression: From Epidemiological to Clinical Evidence

Depression is a frequent mental disorder with a substantial contribution to years lived with disability worldwide. In the search for new treatment targets, the immune system's contribution to the pathogenesis of depression has received increased attention as immune activation has been associated with depression in various epidemiological and case-control studies. Epidemiological studies have shown that immune exposures such as severe infections and autoimmune disorders increase the risk of depression. Furthermore, immune system activation has been indicated in case-control studies of depression revealing higher levels of key pro-inflammatory cytokines among patients with depression than healthy controls, particularly in blood and to some extent in the cerebrospinal fluid. Moreover, brain imaging studies indicate increased microglial activity during depression, and gut microbiota studies have documented alterations of gut microbiota composition to be associated with depression. Based on findings from animal and human studies, several immune-mediated molecular mechanisms have been suggested to underlie the association between increased immunological activity and depression. However, the research is challenged by the heterogeneity of the depression diagnosis and - to some extent - the precision of currently available technology for immune biomarker quantification, particularly regarding the assessment of low-grade neuroinflammation. Nonetheless, an enhanced understanding of the complex interactions between the immune system and the brain in the context of depression could pave the way for precision medicine approaches with immune-modulating treatment as a promising additional option in the treatment of depression.

A Comparison of IgG Index and Oligoclonal Band in the Cerebrospinal Fluid for Differentiating between RRMS and NMOSD

As the oligoclonal band in the cerebrospinal fluid (CSF-OCB) in predicting relapsing-remitting multiple sclerosis (RRMS) is less sensitive in Asian populations than that in westerners, it remains elusive whether the IgG index could serve as an alternative. The purpose of this study was to compare these two methods of differentiating between RRMS and neuromyelitis optica spectrum disorder (NMOSD) in Chinese patients. A total of 171 patients (81 RRMS and 90 NMOSD) were retrospectively recruited, of whom 82 (56 RRMS and 26 NMOSD) received the CSF-OCB testing additionally. When the onset age was ≤38.5 years, IgG index with the threshold of 0.67 had a significant agreement (k = 0.4, p < 0.001) with the diagnosis while CSF-OCB failed to discriminate (k = 0.1, p = 0.578). However, when the onset age was >38.5 years, both IgG index with the threshold of 0.8 and CSF-OCB were moderately consistent with the diagnosis (both k > 0.4, p < 0.05). In total, our optimized algorithm had the sensitivity, specificity, and predictive accuracy of 0.778, slightly outperforming the CSF-OCB model. Accordingly, a combination of the onset age and IgG index could serve as an alternative to CSF-OCB for differentiating between RRMS and NMOSD in Chinese patients.

Immunological investigations of the cerebrospinal fluid in patients with recent onset psychotic disorders: A study protocol

BACKGROUND

Though many previous studies have indicated immunological alterations in psychotic disorders, the role and prevalence of neuroinflammation is still unknown. Studies previously investigating immune related biomarkers in the cerebrospinal fluid (CSF) of these patients are mainly small studies on few markers, and many have not compared patients to healthy controls.

METHODS

We will conduct a large case-control study including at least 100 patients with recent onset psychotic disorders and 100 sex- and age matched healthy controls. The cases will include patients diagnosed with a psychotic disorder according to ICD-10 (F20/F22-29) within a year prior to inclusion. We will collect both CSF, blood and fecal samples, to gain insight into possible immunological alterations. The psychopathology of all participants will thoroughly be evaluated using the SCAN interview, and multiple rating scales covering different symptom groups. All participants will partake in a detailed neurological examination, including the Neurological Evaluation Scale assessing neurological soft signs. Additionally, we will assess cognitive functioning, evaluate quality of life and level of functioning, and collect data on a broad array of possible confounders. Our primary outcomes will include CSF leucocytes, CSF/serum albumin ratio, CSF total protein, IgG index, CSF levels of IL-6 and IL-8, and presence of antineuronal autoantibodies in CSF and blood. For our secondary outcomes, exploratory analyses will be performed on a broader panel of neuroimmunological markers. All participants will be invited for a follow-up visit to assess longitudinal changes. The current study is part of a larger CSF biobank build-up for severe mental disorders (PSYCH-FLAME).

DISCUSSION

This study will represent the largest investigation of CSF in patients with psychotic disorders compared to healthy controls to date. We expect the study to contribute with new, important knowledge on pathophysiological mechanisms, and to help pave the way for future investigations of individualized treatment options.

TRIAL REGISTRATION

The study is approved by The Regional Committee on Health Research Ethics (Capital Region, j.no: H-16030985) and The Danish Data Protection Agency (j.no: RHP-2016-020, I-Suite no.: 04945).

Cognitive Decline in Multiple Sclerosis Is Related to the Progression of Retinal Atrophy and Presence of Oligoclonal Bands: A 5-Year Follow-Up Study

Background: Brain atrophy, which is associated with cognitive impairment and retinal nerve fiber layer (RNFL) atrophy, is the main biomarker of neurodegeneration in multiple sclerosis (MS). However, data on the relationship between inflammatory markers, such as oligoclonal bands (OCBs) in the cerebrospinal fluid (CSF), and cognition, RNFL atrophy, and brain atrophy are scarce. The aim of this study was to assess the influence of RNFL thickness, brain atrophy markers, intrathecal OCBs, and the immunoglobulin G (IgG) index on cognitive decline over a 5-year period in patients with MS. Methods: This prospective, single-center, observational cohort study included 49 patients with relapsing MS followed up over 5 years. At baseline, the patients underwent brain magnetic resonance imaging (MRI). Cognitive evaluation was performed using the Brief International Cognitive Assessment for MS (BICAMS), and RNFL thickness was assessed using optical coherence tomography (OCT). OCBs and IgG levels in the CSF were evaluated at baseline. The BICAMS, OCT, and MRI findings were re-evaluated after 5 years. Results: A significant reduction in information processing speed, visual learning, temporal RNFL thickness, the Huckman index, and third ventricle mean diameter was found in all 49 patients with relapsing MS over the observation period (p < 0.05). Of the patients, 63.3% had positive OCBs and 59.2% had elevated IgG indices. The atrophy of the temporal segment and papillomacular bundle and the presence of OCBs were significantly related to a decline in information processing speed in these patients (p < 0.05). However, brain atrophy markers were not found to be significant on the general linear models. Conclusions: RNFL atrophy and the presence of OCBs were related to cognitive decline in patients with MS over a 5-year follow-up period, thereby suggesting their utility as potential biomarkers of cognitive decline in MS.

Absence of B Cells in Brainstem and White Matter Lesions Associates With Less Severe Disease and Absence of Oligoclonal Bands in MS

Objective

To determine whether B-cell presence in brainstem and white matter (WM) lesions is associated with poorer pathological and clinical characteristics in advanced MS autopsy cases.

Methods

Autopsy tissue of 140 MS and 24 control cases and biopsy tissue of 24 patients with MS were examined for CD20⁺ B cells and CD138⁺ plasma cells. The presence of these cells was compared with pathological and clinical characteristics. In corresponding CSF and plasma, immunoglobulin (Ig) G ratio and oligoclonal band (OCB) patterns were determined. In a clinical cohort of 73 patients, the presence of OCBs was determined during follow-up and compared to status at diagnosis.

Results

In 34% of active and 71% of mixed active/inactive lesions, B cells were absent, which correlated with less pronounced meningeal B-cell infiltration (p < 0.0001). The absence of B cells and plasma cells in brainstem and WM lesions was associated with a longer disease duration (p = 0.001), less frequent secondary progressive MS compared with relapsing and primary progressive MS (p < 0.0001 and p = 0.046, respectively), a lower proportion of mixed active/inactive lesions (p = 0.01), and less often perivascular T-cell clustering (p < 0.0001). Moreover, a lower CSF IgG ratio (p = 0.006) and more frequent absence of OCBs (p < 0.0001) were noted. In a clinical cohort, numbers of patients without OCBs in CSF were increased at follow-up (27.4%).

Conclusions

The absence of B cells is associated with a favorable clinical and pathological profile. This finding may reflect extremes of a continuum of genetic or environmental constitution, but also a regression of WM humoral immunopathology in the natural course of advanced MS.

Anti-CD20 B Cell Treatment for Relapsing Multiple Sclerosis

Several clinical trials have demonstrated the efficacy of lytic therapies targeting B cells in the treatment of relapsing multiple sclerosis (MS). More modest efficacy has been noted in the primary progressive subtype of MS. Clinical success has increased interest in the role of B cells in the pathogenesis of MS and in ways to potentially improve upon current B cell therapies. In this mini review, we will critically review previous and ongoing clinical trials of anti-CD20 monoclonal antibodies in MS, including rituximab, ocrelizumab, ofatumumab, and ublituximab. Side effects and adverse event profiles will be discussed. Studies examining the proposed mechanisms of action of B cell depleting therapies will also be reviewed.

Epstein-Barr Virus and Multiple Sclerosis

Multiple sclerosis (MS) is a neurologic disease affecting myelinated nerves in the central nervous system (CNS). The disease often debuts as a clinically isolated syndrome, e.g., optic neuritis (ON), which later develops into relapsing-remitting (RR) MS, with temporal attacks or primary progressive (PP) MS. Characteristic features of MS are inflammatory foci in the CNS and intrathecal synthesis of immunoglobulins (Igs), measured as an IgG index, oligoclonal bands (OCBs), or specific antibody indexes. Major predisposing factors for MS are certain tissue types (e.g., HLA DRB1*15:01), vitamin D deficiency, smoking, obesity, and infection with Epstein-Barr virus (EBV). Many of the clinical signs of MS described above can be explained by chronic/recurrent EBV infection and current models of EBV involvement suggest that RRMS may be caused by repeated entry of EBV-transformed B cells to the CNS in connection with attacks, while PPMS may be caused by more chronic activity of EBV-transformed B cells in the CNS. In line with the model of EBV's role in MS, new treatments based on monoclonal antibodies (MAbs) targeting B cells have shown good efficacy in clinical trials both for RRMS and PPMS, while MAbs inhibiting B cell mobilization and entry to the CNS have shown efficacy in RRMS. Thus, these agents, which are now first line therapy in many patients, may be hypothesized to function by counteracting a chronic EBV infection.

IgG Index Revisited: Diagnostic Utility and Prognostic Value in Multiple Sclerosis

Objective: Early and accurate diagnosis of multiple sclerosis (MS) remains a clinical challenge. The main objective is to evaluate the diagnostic and prognostic value of the routinely performed immunoglobulin G (IgG) index for MS patients in the Asian population.

Methods: A retrospective study was conducted among a cohort of clinically isolated syndrome (CIS) patients in China with known oligoclonal band (OCB) status and IgG index at baseline. We first evaluated the predictive value of IgG index for OCB status. Secondly, the diagnostic utility and prognostic value of IgG index alone were tested. Lastly, we incorporated IgG index into the 2017 McDonald criteria by replacing OCB with either “IgG index or OCB” (modified criteria 1), “IgG index and OCB” (modified criteria 2), or “IgG index” (modified criteria 3). The diagnostic utility of different criteria was calculated and compared.

Results: In a CIS cohort in China (n = 105), IgG index > 0.7 forecasted OCB positivity (X² = 22.90, P < 0.001). An elevated IgG index was highly prognostic of more clinical relapses [1-year adjusted odds ratio [OR] = 1.32, P = 0.015; 2-years adjusted OR = 1.69, P = 0.013] and Expanded Disability Status Scale worsening (1-year adjusted OR = 1.76, P = 0.040; 2-years adjusted OR = 1.85, P = 0.032). Under the 2017 McDonald criteria (Positive Likelihood Ratio = 1.54, Negative Likelihood Ratio = 0.56), an IgG index > 0.7 in CIS patients increased the likelihood of developing MS within 2 years, either when OCB status was unknown (Positive Likelihood Ratio = 2.11) or with OCB positivity (Positive Likelihood Ratio = 2.11) at baseline; An IgG index ≤ 0.7, along with a negative OCB, helped rule out the MS diagnosis (Negative Likelihood Ratio = 0.53).

Conclusions: IgG index > 0.7 predicts OCB positivity at the initial attack of MS and is prognostic of early disease activity. IgG index serves as an easily-obtainable and accurate OCB surrogate for MS diagnosis in the Asian population.