Background and Hypothesis In response to Health Canada’s March 2020 directive, patients on clozapine for over 12 months were allowed to extend hematological testing intervals from 4 to 8 weeks during the COVID-19 pandemic. We hypothesized that this change would not affect the timely detection of hematological abnormalities in patients with severe mental illness. Study Design A chart review was conducted of patients at the Royal Ottawa who were prescribed clozapine from March 2019 to March 2021. We analyzed clinical and hematological data from electronic health records and Clozaril Support and Assistance Network database to compare occurrences of hematological abnormalities [leukopenia (white blood cell count <3.5 × 109/L) and agranulocytosis (absolute neutrophil count <0.5 × 109/L)] from March 17, 2020 to March 16, 2021, between standard and extended monitoring protocols using binomial logistic and zero-inflated negative binomial regressions. Study Results Of 621 patients, 196 were on extended blood monitoring, and 425 followed standard blood monitoring. Clozapine dose did not differ between groups (standard: 370 ± 201 mg; extended: 352 ± 172 mg; P = .14, ds = 0.10). Clozapine treatment duration up to March 2021 was 12.6 ± 8.3 years, with the extended group (10 ± 7.9 years) having a significantly (P < .01, ds = 0.50) shorter duration than the standard (14 ± 8.2 years). Extended monitoring did not significantly impact likelihood of detecting hematological abnormalities (OR = 0.83, 95% CI [0.58,1.41], P = .55) after controlling for age, sex, total bloodwork, and other psychotropics associated with neutrophil counts (ie, valproate, olanzapine). No patient on the extended regimen developed agranulocytosis. Conclusions Reducing blood monitoring frequency in patients on clozapine for more than 12 months did not compromise detection of hematological abnormalities.

中文翻译：

---

评估氯氮平治疗的精神分裂症患者血液监测频率的减少和血液学异常的检测：来自 COVID-19 大流行的图表回顾研究


背景和假设 根据加拿大卫生部 2020 年 3 月的指令，在 COVID-19 大流行期间，允许使用氯氮平超过 12 个月的患者将血液学检测间隔从 4 周延长至 8 周。我们假设这一变化不会影响及时发现严重精神疾病患者的血液学异常。研究设计 对皇家渥太华医院 2019 年 3 月至 2021 年 3 月期间服用氯氮平的患者进行了图表审查。我们分析了电子健康记录和氯氮平支持和援助网络数据库中的临床和血液学数据，以比较血液学异常的发生情况[白细胞减少症] 2020 年 3 月 17 日至 2021 年 3 月 16 日，在使用二项式逻辑和零膨胀负二项式回归。研究结果 在 621 名患者中，196 名患者接受了扩展血液监测，425 名患者接受了标准血液监测。氯氮平剂量在各组之间没有差异（标准：370 ± 201 mg；扩展：352 ± 172 mg；P = .14，ds = 0.10）。截至 2021 年 3 月的氯氮平治疗持续时间为 12.6 ± 8.3 年，延长组（10 ± 7.9 年）的持续时间显着（P < .01，ds = 0.50）短于标准组（14 ± 8.2 年）。在控制年龄、性别、总血量和其他与中性粒细胞计数相关的精神药物（即，丙戊酸、奥氮平）。延长治疗方案中没有患者出现粒细胞缺乏症。 结论 减少服用氯氮平超过 12 个月的患者的血液监测频率不会影响血液学异常的检测。