Table 1

Methodological characteristics of adherence studies

A01Does the study use a prescription dispensation data design (vs dispensation-only data design)?
Does the design use the date of the first prescription (dispensed or not) as the index date to start the follow-up time? Does the design account for primary non-adherence (not filling the first prescription) or early non-adherence (not filling several initial prescriptions with a subsequent restart)? Is the follow-up censored when the doctor discontinues the prescription?
A02Do the sociodemographic and clinical criteria for patient selection allow an approximate representation of the general population of patients with NVAF?
Are the age and sex selection criteria specified? Are the age, sex, deprivation or other relevant sociodemographic characteristic sufficiently similar to the general population of patients with NVAF for the PDC/MPR figures to be generalisable? Is the diagnosis specified? Is the diagnosis (inclusion/exclusion criteria for selecting patients with NVAF) sufficiently similar to the general population of patients with NVAF for the PDC/MPR figures to be generalisable? Are thrombotic risk, bleeding risk and previous stroke history sufficiently similar to the general population of patients with NVAF for the PDC/MPR figures to be generalisable? Are comorbidities, concomitant treatments and other relevant clinical characteristics sufficiently similar to the general population of patients with NVAF for the PDC/MPR figures to be generalisable?
A03Is there a baseline (lookback) period before index date of at least 12 months?
Is a continuous health plan coverage period of at least 12 months before the index date required for inclusion? Is a continuous period of at least 12 months before the index date used to obtain information about the baseline cohort characteristics?
A04Does the study use a new-user design (vs prevalent or experienced user design)?
Is the study designed as a ‘new user’ or ‘incident’ design excluding prevalent users? Has the design searched for at least 12 months before the index date to exclude previous OAC users? Are ‘false’ new users (new users of one OAC but experienced with another OAC) excluded? Can a switcher from one OAC be selected as a ‘case’ for another different OAC?
A05Does the design avoid requiring a minimum no of treatments filled for inclusion?
If the study uses a dispensation-only refill database, does the inclusion criteria require at least two filled prescriptions for inclusion? Do the inclusion criteria require a period of treatment for inclusion?
A06Is there a fixed time window for follow-up days?
Is there a fixed time window of at least 12 months for follow-up? The design avoids the use of the last refill as a date for censoring follow-up (occasionally called ‘prescription based’ design)? Is a continuous coverage period health plan after the index date required for inclusion? Does this period cover the pre-established fixed time follow-up window?
A07Does the design avoid censoring non-persistent patients and switchers?
Does the design avoid censoring days of follow-up if a patient discontinues before the end of the fixed-time follow-up window (except for loss of coverage, death or doctor’s discontinuation)? Does the design avoid censoring days of follow-up if a patient switches to another OAC before the end of the fixed-time follow-up window (except for lost of coverage, death or doctor’s discontinuation)?
A08Does the study account for periods of immeasurable time?
Does the study account for (acute or chronic) hospitalisation days, assuming that patients were provided with and were fully adherent to during a hospital stay? Alternatively, does the study censure for hospitalisation days?
A09Does the study account for stockpiling?
If days covered by one filled prescription filled overlap with another fill, does the study allow the patient to stockpile overlapping prescription periods incorporating the days covered by the second treatment after the end of the days covered by the first?
A10Is the days’ supply measure capped at 1 or 100%?
If the no of days of medication supplied in the observation period is higher than the no of days in the observation period, is the days’ supply measure capped at 1 or 100%?
  • MPR, medication possession ratio; NVAF, non-valvular atrial fibrillation; OAC, oral anticoagulant; PDC, proportion of days covered.