Table 1 Methods of assessing adherence
Measured directlyConfirm drug use and doseMisleading if drug taken prior to testing
Biochemical*Less subject to biasLimited intervals that can be monitored
Little information regarding use over time
Insensitive to inhaled drug
Limited availability and costly
Measured indirectly
Physician’s estimate and patient self-reportEasy to obtainUnreliable
Pharmacy records filling prescriptionConfirm filling prescriptionNeed centralised pharmacy records
Pharmacy database can be incomplete
Pill count or inhaler weighing†Easy to obtainOverestimate compliance
Correlate well with other methods of measurement
Therapeutic outcomeEasy to obtainClinical outcomes can depend on other factors
Electronic monitoring†Helps explain how medications were takenExpensive and not adapted to all inhalation devices
  • *Measurement includes blood levels or urinary excretion of the medication, a metabolite or a marker.

  • †It does not verify that the medicine was ingested.