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Outcomes Associated With Primary and Secondary Nonadherence to Cholesterol Medications

This study evaluates the impact of primary and secondary nonadherence to cholesterol medication on low-density lipoprotein levels, emergency department visits, and hospitalizations.
Published Online: Apr 18,2016
Janet Shin Lee, PhD; Geoffrey Joyce, PhD; and Jeffrey McCombs, PhD
ABSTRACT

Objectives: To examine the impact of primary nonadherence (PNA) and secondary nonadherence (SNA) to cholesterol medication on clinical outcomes.
Methods: This retrospective cohort study used electronic medical record data from a large managed care organization, and includes patients newly prescribed cholesterol medication(s) between December 1, 2009, and February 28, 2010. The date the prescriber ordered the initial cholesterol prescription was defined as the index date. Patients were required to be aged at least 18 years, and have continuous pharmacy benefits for 12 months before and 18 months after the index date. PNA was defined as failure to fill the initial prescription within 180 days of the index date. SNA was defined as having a medication possession ratio of <80%. Study outcomes included changes in low-density lipoprotein (LDL) values from baseline, emergency department (ED) visits, and hospitalizations.
Results: Of the 13,415 patients included in the study, 10% were primary nonadherent and 53% were secondary nonadherent to their cholesterol medication. After adjusting for patient and physician characteristics, post index LDL values in primary and secondary nonadherent patients were significantly higher than in adherent patients by 41 mg/dL and 24 mg/dL, respectively. Risk of ED visits was significantly higher among primary and secondary nonadherent members relative to adherent members (hazard ratio [95% CI]: 1.25 [1.04-1.50] for PNA; 1.28 [1.15-1.43] for SNA).
Conclusions: Better primary and secondary adherence was directly related to improvements in short-term clinical outcomes. This study provides evidence that clinical interventions should target both primary and secondary nonadherent patients in a timely fashion.

Am J Pharm Benefits. 2016;8(2):54-60

PRACTICAL IMPLICATIONS
This study uses pharmacy and medical claims data and laboratory results to demonstrate the relative impact of primary and secondary nonadherence to cholesterol medication on short-term clinical outcomes of low-density lipoprotein (LDL) levels, emergency department (ED) visits, and hospitalizations.
  • Both primary nonadherence and secondary nonadherence to cholesterol medications are considerably high at 10% and 53%, respectively.
  • Relative to adherent patients, both primary and secondary nonadherent patients achieve smaller decreases in LDL levels and experience higher risk of ED visits.
  • Clinical adherence interventions should target both primary and secondary nonadherent patients in a timely fashion.


Primary nonadherence (PNA) is defined as the failure to fill the initial prescription, whereas secondary nonadherence (SNA) refers to patients taking insufficient doses required to experience a therapeutic effect, missing doses or discontinuing therapy early. Although SNA can be easily measured using pharmacy claims data, PNA has only recently become more readily observable with the increased availability of the electronic medical record (EMR). Nearly half of all patients on chronic medications are secondary nonadherent and an estimated 20% of patients discontinue therapy after the first prescription.1,2 In addition, an estimated 20% to 35% of patients are primary nonadherent, depending on the medication class.3,4

Most medication nonadherence research has focused on risk factors associated with SNA, while identified risk factors of PNA have only begun appearing in the literature.3 However, the association between PNA and clinical outcomes is relatively unknown compared with the association between SNA and clinical outcomes.5-8 Furthermore, the impact of PNA on clinical outcomes relative to SNA has not yet been quantified. The challenge with evaluating the relationship between adherence and clinical outcomes is the potential of unobserved confounders that may bias study results. Adherent patients may also be more likely to exercise regularly, eat better, and participate in other health-promoting activities.

The objective of this study was to evaluate the impact of PNA and SNA to cholesterol medication on clinical outcomes, such as changes in low-density lipoprotein (LDL), emergency department (ED) visits, and hospitalizations. This study used EMR data from a large, integrated health plan and included electronic prescribing data. Using the rich pharmacy and medical claims data and laboratory data available in EMR data should offer better insight into the effects of PNA and SNA, insight that is less likely to be confounded by unobserved differences across adherence groups.

METHODS

Study Design and Setting
This retrospective cohort study was conducted at a large managed care organization providing comprehensive healthcare to an estimated 3.4 million current members at its 14 medical centers located throughout Southern California. The internal institutional review board approved this study. The majority of healthcare services and prescriptions are provided to members within its integrated system.

Prescriptions are entered into the EMR system and this information is electronically sent to the pharmacy, including information identifying the prescribing physician. Once the patient checks in at the pharmacy, the prescription is released from the queue and filled while the patient waits.

The EMR also includes data on patient demographics, outpatient and inpatient diagnoses, procedures, laboratory results, and prescription records. Geocoded socioeconomic data based on census-track data are also available in the patient’s EMR. Data on the characteristics of the prescribing physician are also available within the data system.




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