Institute for Health Research, Kaiser Permanente Colorado, Denver, USA.
Ann Pharmacother. 2011 Sep;45(9):1053-60. doi: 10.1345/aph.1Q146. Epub 2011 Aug 18.
Many medication adherence metrics are based on refill rates determined from pharmacy claims databases. However, these methods do not incorporate assessment of nonadherence to new prescriptions when those prescriptions are never dispensed (primary nonadherence), or dispensed only once (early nonpersistence). As a result, published studies may overestimate adherence, but the extent of overestimation posed by not considering patients with primary nonadherence and early nonpersistence has not been assessed.
To estimate the magnitude of misestimation in adherence estimates that results from not including patients with primary nonadherence and early nonpersistence.
We conducted a retrospective cohort study of 15,417 patients enrolled in an integrated health care delivery system who were newly prescribed an antihypertensive, antidiabetic, or antihyperlipidemic medication. We linked prescription orders to medication dispensings. Based on dispensing and refill rates, we stratified patients into primary nonadherent, early nonpersistent, and ongoing dispensings groups. Adherence was estimated using the proportion of days covered (PDC). Standardized observation periods were applied across all groups.
A total of 1142 (7.4%) patients were primarily nonadherent, 3356 (21.8%) demonstrated early nonpersistence, and 10,919 (70.8%) patients received ongoing dispensings, with a mean PDC of 84%. Not including primarily nonadherent and early nonpersistent patients in calculations resulted in adherence estimates overestimated by 9-18%.
When medication adherence is estimated from pharmacy claims databases, adherence estimates are substantially inflated because primarily nonadherent and early nonpersistent patients are not included in the estimations. An implication of this incorrect estimation is potential distortion of the true relationship between medication adherence and clinical outcomes.
许多药物依从性指标都是基于从药房索赔数据库中确定的续药率。然而，这些方法并未纳入对新处方不依从（主要不依从）或仅配一次药（早期不持续）的评估。因此，已发表的研究可能高估了依从性，但由于不考虑主要不依从和早期不持续的患者而导致的估计值高估程度尚未得到评估。
估计不包括主要不依从和早期不持续患者导致的依从性估计值的高估程度。
我们对在综合医疗服务系统中新开抗高血压、抗糖尿病或调脂药物的 15417 名患者进行了回顾性队列研究。我们将处方订单与药物配药相关联。根据配药和续药率，我们将患者分为主要不依从、早期不持续和持续配药组。使用比例用药天数（PDC）估计依从性。所有组均应用标准化观察期。
共有 1142 名（7.4%）患者为主要不依从，3356 名（21.8%）患者表现出早期不持续，10919 名（70.8%）患者接受持续配药，平均 PDC 为 84%。在计算中不包括主要不依从和早期不持续的患者，会导致依从性估计值高估 9-18%。
当从药房索赔数据库中估计药物依从性时，由于未将主要不依从和早期不持续的患者纳入估计值中，因此依从性估计值会大大膨胀。这种错误估计的一个含义是药物依从性与临床结果之间的真实关系可能会被扭曲。
