Multi-Site Evaluation of Immunoassays for Antipsychotic Drug Measurement in Clinical Samples

Atypical antipsychotic drugs are frequently used in the treatment of serious mental illness (SMI), specifically schizophrenia and bipolar disorder. Adherence to these prescribed drug regimens is a challenge to successful treatment with these drugs. For some of the more common drugs in this class, novel turbidimetric immunoassays have been developed for therapeutic drug monitoring (TDM) to aid in the management of patients prescribed these drugs.

Immunoassays for aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, and risperidone were set up at 2 centers: Johns Hopkins Hospital (JHH) on the Roche Cobas® c501, and the Hospital of the University of Pennsylvania (HUP) on the Beckman AU480. Assay imprecision, limit of quantification (LOQ), functional sensitivity, linearity, and recovery were assessed. Remnant clinical samples were obtained from a reference laboratory (ARUP), and immunoassay results were compared with those obtained by LC-MS/MS.

Imprecision at both sites for all analytes and concentrations tested was <10%. The manufacturer's LOQ was confirmed for each assay, and the functional sensitivity for each assay was found to be lower than the LOQ. All assays were found to be linear over the measuring range, with recoveries ranging from 91% to 123%. For method comparison, Deming regression slopes were found to be between 0.84 to 1.28.

The immunoassays evaluated here are suitable for quantifying drug concentrations to be used in TDM for all 6 drugs. Commercialization of these assays will enable increased access for TDM in psychiatric patient management.