Table 1.

Advantages and Disadvantages of Different Methods to Measure Adherence in COPD

	Advantages	Disadvantages
Direct measurements
PDC	Easy to use, inexpensive	Does not always reflect the correct inhalation
Smart apps	Provide accurate use and can detect inhaler errors	Expensive compared to other methods Need of technology-engaged patients
Pharmacy records	Provides evidence of drug refill patterns	Does not always reflect that the patient took the correct dose
Indirect measurements
Morisky-Green	Well validated in COPD	Not specific for inhaled therapies
Batalla	Validated in COPD	Reflects patient’s understanding of disease
TAI	Validated in COPD Specifically designed for inhaled therapies. Provides information on causes of lack of adherence	Low AUC for detection of non-adherent patterns

Abbreviations: PDC, proportion of days covered (percentage of taken doses/ doses prescribed); TAI, inhaler adherence test.