TY - JOUR
T1 - Comparison of pharmacy-based measures of medication adherence
AU - Vollmer, William M.
AU - Xu, Maochao
AU - Feldstein, Adrianne
AU - Smith, David
AU - Waterbury, Amy
AU - Rand, Cynthia
N1 - Funding Information:
Conclusions: Many adherence measures require one, or sometimes two, dispensings in order to be defined. Since such measures assume all dispensed medication is used as directed, they have a built in upward bias that is especially pronounced when they are calculated over relatively short timeframes (< 9 months). Less biased measurement strategies that do not require a dispensing event are available, but require additional data to support their validity. Trial registration: The study was funded by grant R01HL83433 from the National Heart, Lung and Blood Institute (NHLBI) and is filed as study NCT00414817 in the clinicaltrials.gov database.
PY - 2012
Y1 - 2012
N2 - Background: Pharmacy databases are commonly used to assess medication usage, and a number of measures have been developed to measure patients adherence to medication. An extensive literature now supports these measures, although few studies have systematically compared the properties of different adherence measures. Methods: As part of an 18-month randomized clinical trial to assess the impact of automated telephone reminders on adherence to inhaled corticosteroids (ICS) among 6903 adult members of a managed care organization, we computed eight pharmacy-based measures of ICS adherence using outpatient pharmacy dispensing records obtained from the health plans electronic medical record. We used simple descriptive statistics to compare the relative performance characteristics of these measures. Results: Comparative analysis found a relative upward bias in adherence estimates for those measures that require at least one dispensing event to be calculated. Measurement strategies that require a second dispensing event evidence even greater upward bias. These biases are greatest with shorter observation times. Furthermore, requiring a dispensing to be calculated meant that these measures could not be defined for large numbers of individuals (17-32 % of participants in this study). Measurement strategies that do not require a dispensing event to be calculated appear least vulnerable to these biases and can be calculated for everyone. However they do require additional assumptions and data (e.g., pre-intervention dispensing data) to support their validity. Conclusions: Many adherence measures require one, or sometimes two, dispensings in order to be defined. Since such measures assume all dispensed medication is used as directed, they have a built in upward bias that is especially pronounced when they are calculated over relatively short timeframes (< 9 months). Less biased measurement strategies that do not require a dispensing event are available, but require additional data to support their validity. Trial registration: The study was funded by grant R01HL83433 from the National Heart, Lung and Blood Institute (NHLBI) and is filed as study NCT00414817 in the clinicaltrials.gov database.
AB - Background: Pharmacy databases are commonly used to assess medication usage, and a number of measures have been developed to measure patients adherence to medication. An extensive literature now supports these measures, although few studies have systematically compared the properties of different adherence measures. Methods: As part of an 18-month randomized clinical trial to assess the impact of automated telephone reminders on adherence to inhaled corticosteroids (ICS) among 6903 adult members of a managed care organization, we computed eight pharmacy-based measures of ICS adherence using outpatient pharmacy dispensing records obtained from the health plans electronic medical record. We used simple descriptive statistics to compare the relative performance characteristics of these measures. Results: Comparative analysis found a relative upward bias in adherence estimates for those measures that require at least one dispensing event to be calculated. Measurement strategies that require a second dispensing event evidence even greater upward bias. These biases are greatest with shorter observation times. Furthermore, requiring a dispensing to be calculated meant that these measures could not be defined for large numbers of individuals (17-32 % of participants in this study). Measurement strategies that do not require a dispensing event to be calculated appear least vulnerable to these biases and can be calculated for everyone. However they do require additional assumptions and data (e.g., pre-intervention dispensing data) to support their validity. Conclusions: Many adherence measures require one, or sometimes two, dispensings in order to be defined. Since such measures assume all dispensed medication is used as directed, they have a built in upward bias that is especially pronounced when they are calculated over relatively short timeframes (< 9 months). Less biased measurement strategies that do not require a dispensing event are available, but require additional data to support their validity. Trial registration: The study was funded by grant R01HL83433 from the National Heart, Lung and Blood Institute (NHLBI) and is filed as study NCT00414817 in the clinicaltrials.gov database.
KW - Adult
KW - Asthma
KW - Inhaled corticosteroids
KW - Medication adherence
KW - Methodology
KW - Randomized clinical trial
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U2 - 10.1186/1472-6963-12-155
DO - 10.1186/1472-6963-12-155
M3 - Article
C2 - 22691240
AN - SCOPUS:84861994989
SN - 1472-6963
VL - 12
JO - BMC health services research
JF - BMC health services research
IS - 1
M1 - 155
ER -