1 Centers for Medicare & Medicaid Services, Washington, DC.
2 University of North Carolina Eshelman School of Pharmacy, Chapel Hill.
J Manag Care Spec Pharm. 2017 Mar;23(3):337-345. doi: 10.18553/jmcp.2017.23.3.337.
In 2001, the North Carolina (NC) Medicaid program reduced the number of days prescription supply that enrollees could fill from 100 days to 34 days and increased copayments for brand-name medications. Previous work has shown that a change in these policies led to a decrease in medication adherence from 2.9 to 8.0 percentage points in specific populations with chronic conditions. Studies have also shown that days supply limits and copayment increases have heterogeneous effects based on enrollees' baseline characteristics, including baseline adherence. However, this phenomenon has not been studied in the Medicaid population. We undertook this study to assess the heterogeneous effect of the NC Medicaid policy changes in groups with varying levels of baseline adherence.
To examine whether restrictions on days supply had heterogeneous effects in subgroups defined by medication adherence before the policy changes.
A partial difference-in-difference-in-differences model with fixed effects was used to compare medication adherence before and after the NC Medicaid policy changes among Medicaid enrollees subject to the policy changes because of their use of long prescriptions (> 40 days) as compared with (a) NC Medicaid enrollees using short prescriptions (< 40 days) before policy adoption, as well as (b) Medicaid enrollees in Georgia restricted to a 31 days supply through the study period. Medicaid enrollees were included if they filled a prescription for 1 of the following medication classes: antihypertensives, lipid-lowering drugs, or antipsychotics. The effect of the policy changes on medication adherence, calculated using the proportion of days covered (PDC) each quarter by baseline adherence level and clinical condition group, was studied. Average adherence levels over the 18-month prechange period were used to stratify individuals into 3 baseline adherence groups: fully adherent (PDC ≥ 80%), partially adherent (50%-79%), and nonadherent (PDC ≤ 50%).
Enrollees fully adherent at baseline observed a 2.0 (P = 0.001) and 1.2 (P < 0.001) percentage-point decline in adherence for the lipid-lowering drug and antihypertensive cohorts, respectively, in the period after the policy changes. The nonadherent and partially adherent cohorts in the statin group observed an increase in adherence by 1.7-2.6 (P < 0.05) percentage points in the post-index period.
Adherence changes after cost containment policies have a heterogeneous effect on individuals with varying baseline adherence in the Medicaid population. Individuals fully adherent at baseline decreased adherence following policy changes, while individuals partially adherent and nonadherent at baseline either had no change or showed increases in adherence, possibly because of increased contact with pharmacists and clinicians required by shorter prescription lengths. Managed care strategies to control costs should take into consideration the heterogeneity of responses by the enrollees to these policies. Furthermore, policies that consider baseline characteristics of enrollees may be more effective in improving adherence.
This study was partly funded by a grant from the Robert Wood Johnson Foundation for use in data creation. Maciejewski was supported by a Research Career Scientist Award from the Department of Veterans Affairs (RCS 10-391) and owns stock in Amgen. Farley reports consultancy fees from Daiichi Sankyo outside of the conduct of this study. The other authors report no financial or other conflicts of interest related to the subject of this article. The views expressed in this article are those of the authors and do not reflect the position or policy of the Centers for Medicare & Medicaid Services, University of North Carolina at Chapel Hill, Department of Veteran Affairs, or Duke University. Study design and concept were contributed by Amin and Domino, along with Farley and Maciejewski. Domino collected the data, and data interpretation was performed primarily by Amin, along with Domino, with assistance from Farley and Maciejewski. The manuscript was primarily written by Amin, along with Domino, and revised by all the authors.
2001 年，北卡罗来纳州（NC）医疗补助计划将参保者可配药的天数从 100 天减少到 34 天，并增加了名牌药物的 copayment。先前的工作表明，这些政策的变化导致特定慢性病患者的药物依从性从 2.9%下降到 8.0%。研究还表明，基于参保者的基线特征，包括基线依从性，天数供应限制和 copayment 增加具有异质性影响。然而，这种现象尚未在医疗补助人群中进行研究。我们进行这项研究是为了评估 NC 医疗补助政策变化在基线依从性不同的人群中的异质效应。
研究在政策变化之前，根据药物依从性的基线水平，评估对天数供应的限制在亚组中是否具有异质效应。
使用固定效应的部分差异差异差异模型，比较因使用长处方（> 40 天）而受 NC 医疗补助政策变化影响的医疗补助参保者与（a）政策采用前使用短处方（< 40 天）的 NC 医疗补助参保者，以及（b）在研究期间受佐治亚州限制供应 31 天的医疗补助参保者的药物依从性。如果参保者符合以下药物类别之一，他们将被纳入研究：抗高血压药物、降脂药物或抗精神病药物。使用每个季度的比例天数覆盖（PDC）来计算政策变化对药物依从性的影响，按基线依从性水平和临床情况组进行研究。在 18 个月的预变期内的平均依从水平用于将个体分层为 3 个基线依从性组：完全依从（PDC ≥ 80%）、部分依从（50%-79%）和不依从（PDC ≤ 50%）。
基线完全依从的参保者在降脂药物和抗高血压药物队列中分别观察到依从性下降了 2.0（P = 0.001）和 1.2（P < 0.001）个百分点。在他汀类药物组中，不依从和部分依从的队列在指数后期间观察到依从性增加了 1.7-2.6（P < 0.05）个百分点。
在医疗补助人群中，控制成本的政策变化对具有不同基线依从性的个体的依从性变化具有异质效应。基线完全依从的个体在政策变化后降低了依从性，而基线部分依从和不依从的个体则没有变化或显示出依从性增加，这可能是由于较短的处方长度要求增加了与药剂师和临床医生的接触。控制成本的管理式医疗策略应考虑到参保者对这些政策的反应的异质性。此外，考虑参保者基线特征的政策可能更有效地提高依从性。
这项研究部分由罗伯特伍德约翰逊基金会资助用于数据创建。Maciejewski 得到了美国退伍军人事务部研究职业科学家奖（RCS 10-391）的支持，并且拥有 Amgen 的股票。Farley 报告了与 Daiichi Sankyo 的咨询费，与本研究无关。其他作者报告与本文主题无财务或其他利益冲突。本文的观点是作者的观点，不反映医疗保险和医疗补助服务中心、北卡罗来纳大学教堂山分校、美国退伍军人事务部或杜克大学的立场或政策。设计和概念由 Amin 和 Domino 以及 Farley 和 Maciejewski 共同提出。Domino 收集数据，数据解释主要由 Amin 完成，与 Domino 一起，并得到 Farley 和 Maciejewski 的协助。手稿主要由 Amin 撰写，与 Domino 一起，并由所有作者修订。
