Early neutrophil trajectory following clozapine may predict clozapine response – Results from an observational study using electronic health records

• Published in: Brain, behavior, and immunity behavior, and immunity, 2023-10, Vol.113, p.267-274
• Main Authors: Jones, Rowena, Morales-Munoz, Isabel, Shields, Adrian, Blackman, Graham, Legge, Sophie E., Pritchard, Megan, Kornblum, Daisy, MacCabe, James H., Upthegrove, Rachel
• Format: Article
• Language: English
• Subjects: Antipsychotic Agents - therapeutic use; Biomarkers; Clozapine; Clozapine - therapeutic use; Electronic Health Records; Female; Humans; Immune response; Male; Neutrophils; Retrospective Studies; Schizophrenia - drug therapy; Treatment resistant schizophrenia
• ISSN: 0889-1591; 1090-2139
• DOI: 10.1016/j.bbi.2023.07.012

•Patients commencing clozapine divide into different groups based on neutrophil counts.•Early neutrophil trajectory when starting clozapine appears to predict clozapine response.•Neutrophils are increasingly recognised to play key roles in the immune response.•Clozapine’s unique efficacy in TRS may be due to its immune effects.•Neutrophils may be an easily accessible biomarker for treatment response. Clozapine has unique effectiveness in treatment-resistant schizophrenia and is known to cause immunological side-effects. A transient spike in neutrophils commonly occurs in the first weeks of clozapine therapy. There is contradictory evidence in the literature as to whether neutrophil changes with clozapine are linked to treatment response. The current study aims to further examine the neutrophil changes in response to clozapine and explore any association between neutrophil trajectory and treatment response. A retrospective cohort study of patients undergoing their first treatment with clozapine and continuing for at least 2 years identified 425 patients (69% male/31% female). Neutrophil counts at baseline, 3 weeks and 1 month were obtained predominantly by linkage with data from the clozapine monitoring service. Clinical Global Impression- Severity (CGI-S) was rated from case notes at the time of clozapine initiation and at 2 years. Latent class growth analysis (LCGA) was performed to define distinct trajectories of neutrophil changes during the first month of treatment. Logistic regression was then conducted to investigate for association between the trajectory of neutrophil count changes in month 1 and clinical response at 2 years as well as between baseline neutrophil count and response. Of the original cohort, 397 (93%) patients had useable neutrophil data during the first 6 weeks of clozapine treatment. LCGA revealed significant differences in neutrophil trajectories with a three-class model being the most parsimonious. The classes had similar trajectory profiles but differed primarily on overall neutrophil count: with low, high-normal and high neutrophil classes, comprising 52%, 40% and 8% of the sample respectively. Membership of the high-normal group was associated with significantly increased odds of a positive response to clozapine, as compared to the low neutrophil group [Odds ratio (OR) = 2.10, p-value = 0.002; 95% confidence interval (95% CI) = 1.31–3.36]. Baseline neutrophil count was a predictor of response to clozapine at 2 years, with count