Uric acid (UA) is an endogenous antioxidant. Some studies have described that multiple sclerosis (MS) patients have lower serum UA levels than controls, although it has not been established whether UA is primarily deficient, or secondarily reduced due to its scavenging activity. UA has also been proposed as an indicator of disease activity. We, retrospectively, reviewed 478 serum UA levels obtained in 94 MS patients. Ninety samples were collected during a relapse. Correlation between UA levels obtained during a relapse or in a relapse-free period, and comparison between UA and expanded disability status scale (EDSS) score was tested using a two-tailed Student's t test and Spearman correlation coefficients test. UA levels were significantly lower when measured during a relapse (n 90) than in a remission period (n 368) (r -0.16, p 0.003) UA levels measured outside a relapse inversely correlated with EDSS score (r -0.15, p 0.001). Lower uric acid levels in MS patients are associated with clinical relapse. This is the first description of an inverse correlation of serum UA levels with disability as assessed by EDSS score.

Uric acid (UA), a product of purine metabolism, may be an antioxidant, perhaps acting as a scavenger of peroxynitrite. Patients with gout have a reduced incidence of multiple sclerosis (MS). A number of studies found that patients with MS have low serum levels of UA, although it has not been established whether this represents a primary deficit or a secondary effect. UA has also been proposed as a marker of disease activity and response to immunosuppressive or immunomodulatory treatment. We retrospectively reviewed 83 relapsing-remitting or secondary progressive MS patients (64 females and 19 males) followed in our Neurology Unit. We collected data concerning demographic variables as age and sex, and clinical variables as age of onset, clinical type, disease duration, EDSS score and total number of relapses. We considered UA levels in three different situations: during a relapse, during remission period and during remission period under immunomodulatory treatment [Interferon Beta 1a i.m. (Avonex; Biogen Idec Inc., Cambridge, MA, USA), Interferon Beta 1a s.c. (Rebif; Serono Europe Limited, London, UK), Interferon Beta 1b (Betaferon; Bayer Schering Pharma AG, Berlin, Germany) or Glatiramer Acetate (Copaxone; TEVA Neuroscience LLC, Kansas City, MO, USA)]. A Wilcoxon matched pairs test was carried out to determine differences between groups. A P-value less than 0.05 was considered statistically significant. In 33 patients, we were able to compare at least one UA value obtained during a relapse with at least one when remission without treatment. Mean serum UA levels were significantly lower when measured during a relapse (r: 0.39, P: 0.024). In 27 cases, we compared at least one remission value without treatment with at least one obtained during remission and immunomodulatory treatment. Mean serum UA levels significantly increased when determined during Interferon Beta or Glatiramer Acetate therapy (r: 0.84, P < 0.001). Although we do not know exactly whether and how UA is involved in MS pathogenesis, our data suggest that UA might reflect disease activity or treatment response in MS.

Findings of a recent meta-analysis have not supported a role for APOE in MS susceptibility or severity. We have not found, in our data, any influence of this gene in the RRMS response to INFbeta. However, larger series would be required to validate these results.

Our results show no effect of the APOE genotype on the severity of MS measured by MSSS, as a recently published meta-analysis has noticed. So, our data do not support a role for APOE in MS severity, in spite of the seeming influence shown using other measures such as PI. MSSS is probably the best method to measure severity with a single measure of disability and should be used more frequently when performing genetic research.

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