Date of Award
Summer 2024
Document Type
Open Access Dissertation
Department
College of Pharmacy
First Advisor
Chao Cai
Abstract
Background: Schizophrenia is a chronic and serious mental disorder that affects millions of individuals worldwide. A recent study shows the prevalence of schizophrenia globally is about 1%. The primary schizophrenia treatment goal is to effectively manage symptoms and prevent relapses. Antipsychotic medications are very important for the treatment of schizophrenia. However, the prevalence of nonadherence to antipsychotic medication is high, with mean rates reaching 41.2%. In the realm of schizophrenia treatment, two primary categories of medications are utilized: long-acting injectable antipsychotics (LAI) and oral antipsychotic agents (OAP).LAI are administered at intervals spanning from two weeks to several months and have potential to improve medication adherence.
Objectives: The aims of this study were to (1) compare medication adherence between LAI and OAP using a prevalent user design with propensity score matching method; (2) compare medication adherence between LAI and OAP using prevalent new user design with time-dependent propensity score matching method; (3) identify number of latent adherent classes using three observed measures of adherence (PDC, MPR, persistence) and evaluate the effects of predictors on latent class membership using latent variable analysis and multinomial regression analysis.
Methods: This study used a South Carolina Medicaid claims data from 2012 to 2019 to analyze a sample of Medicaid beneficiaries diagnosed with schizophrenia based on the International Classification of Diseases, Ninth & Tenth Revision, Clinical Modification (ICD-9/10-CM) codes. In study aim 1, a prevalent user design was used to analyze the medication adherence among beneficiaries with schizophrenia. Two matched therapy group pairs – (LAI versus OAP) were generated using a 1:1 greedy propensity score (PS) matching procedure. T test was performed to compare the medication adherence of LAI versus OAP. In study aim2, a prevalent new user design by time-dependent propensity score matching was used to analyze the medication adherence among beneficiaries with schizophrenia. ANCOVA was performed to compare the medication adherence of LAI versus OAP. In study aim 3, We employed latent profile analysis (LPA) to identify the optimal number of latent adherent classes based on observed indicators of medication adherence. This determination was made by comparing three key metrics: Akaike's Information Criterion (AIC), Bayesian Information Criterion (BIC), entropy. The indicators, namely proportion of days covered (PDC), medication possession ratio (MPR), persistence and maximum gap were employed in the latent classes estimation. These four observed metrics were collectively used to compute each patient’s conditional probability of being in different latent classes. After each patient’s adherence class membership was determined by the highest conditional probability, we assessed the effects of potential predictors (e.g., LAI versus OAP, age group, gender, race group etc.) on latent class membership using multinomial logistic regression.
Results: In study aim 1, the analytical sample consists of 1,421 beneficiaries treated with LAI and 2,573 beneficiaries treated with OAP. LAI patients showed a higher likelihood of being male (65.9% for LAI vs 52.8% for OAP). More patients receiving OAP belonged to the oldest age group (≥35 years; 66.6% for LAI vs. 72.2% for OAP). A greater proportion of LAI patients identified as Black or African American (57.1% for LAI vs. 45.7% for OAP). A total of 1,327 matched pairs were generated for LAI versus OAP. Based on matched sample, the PDC was higher in the LAI cohort compared to the OAP cohort (0.68 vs. 0.64, p
Conclusion: In the aim 1 and aim 2, patients using LAIs had a significantly higher medication adherence compared to those using OAPs. In the aim 3 of the project, focusing on Medicaid beneficiaries who were currently prescribed with antipsychotics during the patients identification window, under the latent variable framework, we identified four latent adherence classes, which were labeled as “best adherence”, “intermittent adherence”, “early drop-off” and “worst adherence”. The estimated prevalence rates for these adherence classes were 58%, 17%, 9% and 16%, respectively. , 54% of OAP users and 65% of LAI users were labeled as “best adherent”. Adherence to OAP and LAI was not only associated with demographics, but also clinical characteristics. These clinical factors may include the medication side effects, comorbid conditions, treatment history, and response to medication.
Rights
© 2024, Pujing Zhao
Recommended Citation
Zhao, P.(2024). Medication Adherence Between Long-Acting Injectable and Oral Antipsychotic Medications in South Carolina Medicaid Beneficiaries with Schizophrenia. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/7905