Prevalence and frequency of haematological testing in patients initiating clozapine in the USA
By
Katsiaryna Bykov
Mufaddal Mahesri
Krista F Huybrechts
Lauren V Moran
Catherine S Hwang
Junyi Wang
Joyce Lii
Gita A Toyserkani
Esther H Zhou
Cynthia LaCivita
Gerald J Dal Pan
Aaron S Kesselheim
Ameet Sarpatwari
July 10, 2026
Clinical Scorecard: Assessment of the Frequency and Prevalence of Hematological Testing in Patients Starting Clozapine in the United States
At a Glance
Category Detail
Condition Clozapine therapy monitoring Key Mechanisms Routine haematological testing to prevent agranulocytosis Target Population Patients initiating clozapine therapy Care Setting Clinical practice in the USA
Key Highlights
71% of patients had at least one haematological test prior to clozapine initiation. Mean testing rate was 2.2 tests per patient in the first 6 months of treatment. Testing frequency decreased over time, with 1.5 tests per patient during months 13-24. Guideline-Based Recommendations
Diagnosis
Routine haematological monitoring is recommended for patients on clozapine. Management
Weekly monitoring of absolute neutrophil counts (ANCs) is advised during the first 6 months. Monitoring & Follow-up
Patients should undergo regular haematological testing to prevent agranulocytosis. Risks
Inadequate testing may increase the risk of agranulocytosis. Patient & Prescribing Data
Testing adherence was lower than expected, particularly in the first 6 months.
Clinical Best Practices
Ensure compliance with haematological testing recommendations during clozapine therapy. Investigate reasons for low adherence to testing requirements. Related Resources & Content
