Abstract
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.
Highlights
Multiple sclerosis (MS) is a demyelinating disease with a poor outcome if not diagnosed and treated in time [1]
From January 2012 to July 2019, a total of 154 patients were enrolled in the CIS cohort; 115 of them had available immunoglobulin G (IgG) index and oligoclonal band (OCB) data at baseline; 10 were further excluded for reaching an alternative diagnosis during follow-up
Twenty (19%) patients were on immunosuppressive agents at least once during follow-up, including one of the available disease-modifying therapy (DMT) in China, or off-label drugs; two (1.9%) patients had initiated treatment prior to their second-attack and 1 (1.0%) prior to diagnosis of McDonald MS
Summary
Multiple sclerosis (MS) is a demyelinating disease with a poor outcome if not diagnosed and treated in time [1]. CSF analysis, with its ability to detect intrathecally synthesized immunoglobulins, in the form of immunoglobulin G (IgG) index or CSF-specific oligoclonal band (OCB), provide critical information of central nervous system (CNS) inflammation [3, 4]. OCB was not routinely tested for CIS patients in China, partly due to its cost and inadequate recognition among clinicians. IgG index, a quantitative measurement of intrathecal IgG synthesis [5], is routinely and universally performed in all the patients with suspected CIS in China [4, 6]. Given its low cost and easy accessibility, IgG index is still considered a potential candidate for MS diagnosis despite a relatively low sensitivity (50–75% among MS patients) [3]. The prognostic value of IgG index or OCB remains undetermined based on existing evidence [10,11,12,13]
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