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How reliable are reported plasma clozapine levels?
1Clozaril Patient Monitoring System, The Mental Health Research Institute of Victoria, Melbourne, Australia. wrbell99@hotmail.com
The Australian and New Zealand Journal of Psychiatry
|September 5, 2001
Summary
Assaying plasma clozapine levels shows high consistency between laboratories in Australia and New Zealand. Clinicians can trust results regardless of the chosen laboratory or operator for accurate patient monitoring.
Area of Science:
- Clinical Chemistry
- Pharmacology
- Analytical Science
Background:
- Plasma clozapine levels are crucial for optimizing patient dosage.
- Interlaboratory variability in clozapine assays can impact clinical decisions.
Purpose of the Study:
- To evaluate the accuracy and consistency of clozapine plasma assays across different laboratories.
- To assess interlaboratory variability in clozapine measurement.
Main Methods:
- Multi-phase study involving dispatch of plasma samples with known clozapine concentrations to multiple assaying centers.
- Phase II and III involved different concentration ranges and analysis of results.
- Inclusion of samples in purified water and freeze-dried formats.
Main Results:
- Phase II showed some interlaboratory variation, but Phase III yielded concordant results across all centers.
- High consistency was observed with a maximum coefficient of variation of 0.16.
- Measured concentrations were consistently lower than nominal concentrations.
Conclusions:
- Assays for plasma clozapine levels demonstrate high reliability and consistency among laboratories in Australia and New Zealand.
- Clinicians can be confident in the accuracy of clozapine assay results, irrespective of the laboratory or operator.
- The study supports the use of plasma clozapine levels for therapeutic drug monitoring.