Measuring adherence to antipsychotic medications for schizophrenia: Concordance and validity among a community sample in rural China.

BACKGROUND

Despite the abundance of measures to assess medication adherence by persons suffering schizophrenia, few studies have evaluated their concordance and validity against a reference standard in resource-poor community settings. We explored the concordance and validity of several measures to assess antipsychotic medication adherence in a resource-poor community.

METHOD: Based on a random sample of 278 villagers diagnosed with schizophrenia from Liuyang, Hunan Province, China, we used a concordance correlation coefficient (rc) and Kappa statistic to assess agreement among pill counts, refill records, clinician rating, Drug Attitude Inventory (DAI), and the Brief Adherence Rating Scale (BARS). The validity of various measures was evaluated by their concordance and sensitivity/specificity to home-based unannounced pill count (UPC) as the reference standard.

RESULTS

The estimated proportion of adherent patients according to all measures (41% ~ 88%) was substantially higher than identified by UPC (35%). Concordance between any two measures was poor (rc/Kappa mostly <0.30). Validity of various measures also was poor against the UPC (rc < 0.20; Kappa <0.16), although refill records and the structured instruments (BARS) performed better than office-based pill counts and clinician impression. BARS, DAI and clinician rating were not sensitive to changes in adherence and would likely underestimate any program effect.

CONCLUSION

In resource-poor community settings, most measures assessed in this study should not be used alone as they overestimated adherence, underestimated program effect, and had poor validity. A combination of UPC and several other measures may provide more insight into clinical trials and programmatic management.