[Be prepared to define what would constitute strong agreement and the fact that p-values are not necessarily important. I believe this kappa coefficient was statistically significant.]
----- Meeting Notes (4/23/14 12:50) -----pharmacy prescription refillconsider what is actually measure
Neither approach is considered a gold standard, but either can be used to target patients for adherence interventions.
Agreement between Claims-based and Self-reported Adherence Measures in Patients with Type 2 Diabetes
Agreement and Correlation Between Claims-based
and Self-reported Adherence Measures in Patients
with Type 2 Diabetes Mellitus
Mukul Singhal, Brandon K. Bellows, Sudhir Unni,
Department of Pharmacotherapy
Pharmacotherapy Outcome Research Center
• Future Research
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• Medication non-adherence is a complex issue
driven by many factors such as cost, perception of
benefit, forgetfulness, and side effects1
• In type 2 diabetes mellitus (T2DM), adherence to
oral medications varies from 36%-93%2
• Medication adherence is clinically important as
good adherence is associated with improved
outcomes in T2DM1
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1.Dunbar, et al. J Clin Epidemiol. 2001;54:S57–S60.
2.Cramer, et al. Diabetes care. 2004;27(5):1218-1224.
• Self-reported adherence measures are used in practice
• Recall bias is an issue with self-reported adherence.2
• Claims-based measures use prescription refill data to
• Claim-based adherence uses purchasing behavior as a
surrogate for consumption, which may also produce a
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1.Robin, et al. Med Care. 2002;40:794–811.
2.Dunbar, et al. J Clin Epidemiol. 2001;54:S57–S60.
• Self-reported measures often capture intentional and unintentional
aspects of adherence
• Claims-based adherence describes prescription purchasing behaviors
• These adherence measurement approaches may not be correlated, with
most studies showing a weak association.1-2
• In understanding how adherence effects T2DM treatment outcomes, it is
first important to understand the correlations between adherence
measurement approaches in patients treated with diabetes medications
1. Thorpe, et al. Med Care. Apr 2009;47(4):474-481.
2. Garber, et al. Med Care. Jul 2004;42(7):649-652.
• Report the agreement and correlation between pharmacy
claims-based and self-reported adherence measures in
patients with T2DM.
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Study Design & Data
• Historical cohort study and patient survey
• Geisinger Health System (GHS) Electronic Health Record
– Integrated health system in Pennsylvania
– Over 3 million patients and 650 physicians
– Affiliated with Geisinger Health Plan (GHP), one of the
largest rural HMOs in the US
– A third of GHS patients have GHP coverage
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• Patients with T2DM
– Diagnosis per ICD-9 codes, elevated blood glucose/HbA1c, or
• Prescribed any class of anti-diabetic not previously prescribed
(index date) from Nov 1, 2010 to Apr 30, 2011
• Willing to complete survey, with GHP medication claims
data, and taking index-date medication for >30 days
• Exclusion criteria
– Newly prescribed 2+ anti-diabetic classes on index date
Methods: Study Population
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Methods: Adherence Tools
• Claim Based Adherence
– Modified Medication Possession Ratio (mMPR)
– Adherence measured for up to 6 months after index
• Self Reported Adherence
– 5-item Medication Adherence Report Scale (MARS-5)
– Adherence survey conducted 6+ months after index
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Claim based Adherence
Modified Medication Possession Ratio (mMPR)
Total days supplied of the anti-diabetic medication .
# of days between first and last fill+ days supplied on the last claim
• mMPR ≥0.8 considered adherent
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30 days 60 days 90 days 120 days
30 days refill +
30 days refill
30 days refill +
30 days refill
Adherence Calculation Example
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Modified Medication Possession Ratio (mMPR)
Self Reported Adherence
• Medication Adherence Reported Scale -5 (MARS-5)
– I forget to take my diabetes medicine. Would you say this occurred
"Always", "Often", "Sometimes", "Rarely", or "Never"? (Score 1-5)
– I alter the dose of my diabetes medicine. (Score 1-5)
– I stop taking my diabetes medicine for a while. (Score 1-5)
– I decide to miss out on a dose of my diabetes medicine. (Score 1-5)
– I take less diabetes medicine than instructed. (Score 1-5)
• MARS-5 score of 25 was considered adherent; a score <25 was
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1. Farmer et al. Diabet Med. Mar 2006;23(3):265-270.
2. Horne et al.. J Psychosom Res. Dec 1999;47(6):555-567
Methods: Statistical Analysis
– Baseline characteristics, adherence measures
• Kappa coefficient:
– Agreement between the mMPR and MARS-5
• Tetrachoric correlation coefficients:
– correlation between mMPR and MARS-5
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Patients in Geisinger EMR Database with newly prescribed
antidiabetic class Nov 1, 2010 to Apr 30, 2011
Surveyed and provided self-reported adherence data
With anti-diabetic pharmacy claim data in GHP
With pharmacy claims on or after the index day for patient-
reported drug class
Self-reported taking index-drug ≥30 days
Variables Self-reported taking index-drug ≥30
Mean (SD) age 61.1(12.1)
Age 65+ 41%
Mean (SD) baseline BMI (kg/m2) 35.5(7.9)
Mean (SD) baseline HbA1c (%) 8.1(1.6)
Mean (SD) baseline weight (kg) 98.8(22.5)
Anti-diabetic treatment naïve pre-index
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Self reported Vs. Claim Based Adherence
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Self Reported Adherence (MARS-5) Claim Based Adherence (mMPR)
Agreement and disagreement between self
reported and claim adherence (N=166)
Adherent (≥0.8 )
Adherent (25) 97(58.4) 23(13.9)
Non-Adherent (<25) 31(18.7) 15(9.0)
• Slight agreement was observed between claims
based and self reported adherence measures (Kappa
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Range 0–0.20 0.21–0.40 0.41–0.60 0.61–0.80 0.81–1.0
Interpretation Slight Fair Moderate Substantial Perfect
• A significant but weak positive correlation was
observed in the most highly adherent patients
– Tetrachoric correlation coefficient=0.250, p=0.0635)
• There are multiple methods for assessing claims-based and self-reported
adherence – this study is based on one of each type and agreement and
correlation may not be generalizable to other measurement approaches
• Limited external validity - a small sample of patients from Pennsylvania
treated in integrated health system
• Patients asked to recall medication adherence when newly started on
index date drug – concurrent self-reported MARS may have different
association/correlation with mMPR
• Agreement and correlation between these measurement approaches was
weak – conclusions about adherence based on patient report may not
match the conclusions drawn about adherence based on refill data
– Neither is the gold standard
• When interpreting adherence data, is important to consider what
behavior the measurement approach represents
– Important in clinical practice as well as in interpreting results from studies reporting the
associations between adherence and treatment outcomes
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• This study has been used to inform ongoing research that assesses the
impact of adherence on diabetes treatment on weight and glycemic contol
• Future research will more precisely align claims-based and self-reported
adherence measurement periods to reduce potential bias
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Acknowledgement/ Financial disclosure
• This study was funded by a grant from Bristol-Myers Squibb (BMS)
• Geisinger center for survey
• Elizabeth Unni for developing survey contents
• Brian Oberg for data management
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