Predictors of relapse after omalizumab withdrawal in chronic spontaneous urticaria: Role of baseline autoimmunity and hematologic indices: CSU Relapse After Omalizumab Withdrawal

<b>Background:</b> There is currently no accepted biomarker for predicting which patients will experience relapse after discontinuation of omalizumab therapy. <b>Objective:</b> This retrospective study aimed to identify clinical and laboratory markers associated with chronic spontaneous urticaria relapse. <b>Methods:</b> "Relapse" was defined as a urticaria control test score of <12 during the 6-month follow-up after treatment interruption after 24 weeks of therapy. Baseline demographic characteristics and laboratory values, including total immunoglobulin E (IgE), anti-thyroid peroxidase (TPO), C-reactive protein (CRP), and complete blood cell count parameters, were compared between patients who did and patients who did not experience relapse. <b>Results:</b> In the cohort of 43 patients, relapse occurred in 13 (30.2%). There were no significant differences between the patients who relapsed and those who did not relapse with respect to gender, age, disease duration, disease activity, concomitant angioedema, chronic inducible urticaria, atopic comorbidity, total IgE levels, or CRP levels. The median anti-TPO level was significantly higher in the relapsed group (p = 0.039), with an optimal predictive cutoff value of 67 IU/mL, with 62.5% sensitivity and 84.2% specificity (area under the curve 0.753; p = 0.041). Among the hematologic parameters, the mean platelet volume (MPV) was the only variable to differ significantly (p = 0.028), being lower in the relapsed group than in the non-relapsed group, and yielded an optimal cutoff value of 10.25 fL, with 92.3% sensitivity and 34.5% specificity (area under the curve 0.712; p = 0.03). <b>Conclusion:</b> In this retrospective, small-sample study, the anti-TPO level and MPV emerged as exploratory predictors of recurrence; however, their clinical utility requires validation in larger, prospective cohorts before implementation.