Hematological clozapine monitoring with a point-of-care device: A randomized cross-over trial

Clozapine remains the drug of choice for patients with treatment-resistant schizophrenia, who show a response rate of about 50% despite their unresponsiveness to other antipsychotics. Although treatment with clozapine can lead to considerable savings on bed days, the drug is underutilized for several reasons, perhaps most importantly because of the mandatory hematological monitoring. The Chempaq Express Blood Counter (Chempaq XBC) is a point-of-care device providing counts of white blood cells (WBC) and granulocytes based on a capillary blood sampling. A randomized cross-over trial design was used comparing capillary blood sampling using a point-of-care device with traditional venous blood sampling. Patients were randomized to two sequences starting with either capillary or venous blood sampling followed by a repeated sequence. Primary outcome was measured on a 10-cm visual analog scale. Eighty-five patients were included in the test. Eight (9.4%) dropped out before completion. Patients indicated that they found capillary blood monitoring less painful than venous sampling (VAS ratings: 0.55 cm 25–75 percentiles: 0.1–1.4 cm vs. 1.75 cm 25–75 percentiles: 0.7–2.6, p < 0.001). They also felt less inconvenienced by the point-of-care method than the traditional blood sampling, which involved traveling to the laboratory clinical (0.3 cm 25–75 percentiles: 0.05–0.7 vs. 2.3 cm 25–75 percentiles: 0.75–4.5, p < 0.001). For hematological monitoring of clozapine patients a point-of-care device based on capillary blood sampling is better tolerated than traditional venous blood sampling.