Previous epidemiologic studies showed an increased risk of neutralizing antibody (NAb) development against Interferon beta in multiple sclerosis patients who smoke. Cotinine is an easily detectable metabolite of nicotine and, therefore, can be used as an objective surrogate marker for smoking status. We measured cotinine levels in NAb-positive and NAb-negative patients to find a potential association of nicotine consumption and NAb development. Cotinine was measured in 37 patients with known smoking status and in 123 patients with unknown smoking status, all of whom were routinely tested for NAb. Cotinine was detected by an enzyme-linked immunosorbent assay, inhibition assay. We compared cotinine levels by NAb status and tested for the strength of association between cotinine and NAb status. We found a discrepancy between smoking status stated by patients and status defined by cotinine levels in 7 of 37 patients. In both cohorts, together with and without previously known smoking status (n = 160), we found 34% and 39% smokers, respectively, as defined by cotinine levels in NAb-negative and NAb-positive patients (P = 0.511). In our analysis, smoking was not associated with higher risk of NAb development. Moreover, smoking habits stated by patients do not always correlate with cotinine levels.
Keywords: antibodies; cotinine; interferon beta; risk; smoking.