First Use of Clozapine Point of Care Testing in Acute Inpatient Psychiatry: Preliminary Report

Clozapine is the antipsychotic of choice in treatment-resistant schizophrenia. Serum clozapine concentration testing is essential to monitor adherence, adjust dosing, and ensure treatment safety. However, patients who are acutely unwell are frequently reluctant to undergo blood testing requiring venipuncture. Also, conventional laboratory-based measurement of clozapine plasma levels can take days, thus contributing to the suboptimal use of clozapine when it is most needed. We pioneered clozapine whole-blood point of care (POC) testing in the acute inpatient setting in the treatment of a group of actively psychotic patients receiving clozapine during the outbreak of the COVID-19 pandemic. POC clozapine testing using automated homogenous immunoassay requires only finger prick blood sampling and is more acceptable to patients. As it produces results in minutes, clozapine POC testing serves to promptly ascertain adherence with treatment and inform therapeutic dosing. POC testing offered a more practical, less invasive, and quicker alternative to conventional methods of monitoring clozapine levels. Near immediate availability of clozapine levels expedited clinical decisions and helped ensure safe clozapine prescribing to our severely psychotic patients in a time of crisis. By facilitating patients' early safe discharge from the hospital, clozapine POC testing also reduced length of hospitalization.