Measurement of treatment adherence with antipsychotic agents in patients with schizophrenia

Abstract

The importance of medication adherence in sustaining control of schizophrenic symptoms has generated a great deal of interest in comparing levels of treatment adherence with different antipsychotic agents. However, the bulk of the research has yielded results that are often inconsistent. In this prospective, observational study, we assessed the measurement properties of 3 commonly used, pharmacy-based measures of treatment adherence with antipsychotic agents in schizophrenia using data from the Veterans Health Administration during 2000 to 2005. Patients were selected if they were on antipsychotics and diagnosed with schizophrenia (N = 18,425). A gap of ≥30 days (with no filled index medication) was used to define discontinuation of treatment as well as medication “episodes,” or the number of times a patient returned to the same index agent after discontinuation of treatment within a 1-year period. The study found that the 3 existing measures differed in their approaches in measuring treatment adherence, suggesting that studies using these different measures would generate different levels of treatment adherence across antipsychotic agents. Considering the measurement problems associated with each existing approach, we offered a new, medication episode-specific approach, which would provide a fairer comparison of the levels of treatment adherence across different antipsychotic agents.

Measuring Medication Adherence in Patients With Schizophrenia: An Integrative Review

“…Kikkert et al (2011) measured medication adherence in patients with schizophrenia by using the Medication Adherence Questionnaire (MAQ), modified Drug Attitude Inventory (DAI), and the Compliance Rating Scale (CRS). Ren et al (2009) assessed the measurement properties of three commonly used pharmacy-based measures (treatment persistence -TP, medication possession ratio -MPR, and medication compliance -MC) in addition to a new measure -episode-specific approach (ESA) to assess medication adherence with three typical (haloperidol, perphenazine and chlorpromazine) and five atypical (clozapine, olanzapine, quetiapine, risperidone and ziprasidone) antipsychotics. Ren et al (2009) used a gap of ≥30 days (with no filled index medication) to define discontinuation of treatment as well as the number of times a patient returned to the same index agent after discontinuation of treatment within a 1-year period, which they termed medication "episodes."…”

“…Ren et al (2009) assessed the measurement properties of three commonly used pharmacy-based measures (treatment persistence -TP, medication possession ratio -MPR, and medication compliance -MC) in addition to a new measure -episode-specific approach (ESA) to assess medication adherence with three typical (haloperidol, perphenazine and chlorpromazine) and five atypical (clozapine, olanzapine, quetiapine, risperidone and ziprasidone) antipsychotics. Ren et al (2009) used a gap of ≥30 days (with no filled index medication) to define discontinuation of treatment as well as the number of times a patient returned to the same index agent after discontinuation of treatment within a 1-year period, which they termed medication "episodes." Byerly et al (2008) used the Brief Adherence Rating Scale (BARS), a recently developed instrument using the electronic monitoring (EM) tool as a reference standard to evaluate the BARS' reliability validity, sensitivity, and specificity.…”

“…Ren et al (2009) further stated that TP uses only the first medication episode, which combined the single prescription for patients who had one prescription with the first episodes among patients who had two or three medication episodes. Ren et al (2009) indicated that results from TP are problematic because it excludes the second episode among patients with two medication episodes and the second and last episodes among those with three medication episodes. Ren et al (2009) therefore concluded that results based on the TP approach are likely to be biased.…”

“…Ren et al (2009) indicated that results from TP are problematic because it excludes the second episode among patients with two medication episodes and the second and last episodes among those with three medication episodes. Ren et al (2009) therefore concluded that results based on the TP approach are likely to be biased.…”

“…Currently, two methods are used in measuring medication adherence in patients with schizophrenia; objective and subjective methods. Subjective methods are mostly self-reports, informant ratings and clinician ratings and are frequently used in many studies (Byerly, Nakonezny, & Rush, 2008;Clayton et al, 2010;Kikkert et al, 2011;Ren, Herz, Qian, Smith, & Kazis, 2009;Thompson, Kulkarni, & Sergejew, 2000). Objective methods such as electronic monitoring, pill count, pharmacy refill records and plasma levels are also used in studies Byerly et al, 2008;Clayton et al, 2010;Velligan et al, 2009).…”