Clozapine blood level assessment using a point-of-care device: feasibility and reliability

Therapeutic drug monitoring (TDM) is useful to assess clozapine adherence and optimize treatment. However, analysis of venous blood levels by liquid chromatography tandem mass spectrometry (LC-MS/MS) is often logistically complicated and process time is prolonged.

To assess the feasibility and reliability of a new point-of-care device, (MyCare™ Insite), using capillary blood for clozapine therapeutic monitoring.

Matched venous and capillary blood samples were collected from patients treated with clozapine on a stable dose. Samples were analyzed by LC-MS/MS and MyCare Insite Clozapine Test. Clozapine plasma levels were compared between methods using linear regression model. Both patients and treatment team completed questionnaires about the feasibility of blood sampling.

Of the total sample (44 patients, 61% males, mean age 43 ± 12 years), mean daily clozapine dose was 293 ± 134 mg/day. Linear regression model demonstrated high correlation with R ² = 0.83 (p < 0.0001) and mean difference of 26 ± 162 ng/ml. More than 60% of the patients found the clozapine TDM to be important. Most of the participants (58%) favored the capillary sampling and 11% claimed that testing method would affect their adherence to TDM. Moreover, a larger portion (72%) strongly preferred to be tested at the office rather than at the lab.

The point-of-care device offers an accessible and satisfactory measurement of clozapine blood levels. Both patients and healthcare providers reported preference for capillary sampling as well as for the in-office TDM procedure. The immediate results provided by the device can facilitate rapid and informed clinical decisions and therefore improve clozapine treatment outcomes.