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| Measures | Target population(s) | For primary/secondary nonadherence | Advantages | Disadvantages |
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| Direct measures | Patients under single-dose therapy and intermittent administration and who are hospitalized | Both primary and secondary nonadherence | Most accurate
Can provide physical evidence | Generate a Yes/No result only
Intrusive
Varied drug metabolism
Nonquantifiable biomarkers/drug metabolites
Drug-drug interactions and drug-food interactions
Expensive
Require qualified staff and techniques to perform
Bias occurs if patients know the schedule of the tests (white coat adherence) |
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| Measures involving secondary database analysis | Countries that allow refilling prescription;
with centralized computerized system with a consistency among prescribers and dispensers;
more common for research with a large population | Primary nonadherence | Able to assess multidrug adherence
Can identify patients at risk for treatment failure
Provide medication-refilling pattern
Complete dataset used are generally verified by a third party for insurance claim purpose | Assumptions are made (the medication-taking behavior corresponds to prescription refilling and the medications are taken according to prescription)
Fail to identify partial adherence
Fail to identify barriers for the detected nonadherence
Missing out prescriptions, if obtained outside the system
Incomplete records, if drug discontinuation is verbally advised by prescriber |
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| Measures involving Electronic Medication Packaging (EMP) devices | Studies with small population
As reference standard to validate other measures | Secondary nonadherence | Highly accurate
Identify medication-taking pattern
Identify partial adherence | Expensive
Technical supports required
Overestimation if patients accidently or purposefully actuate the container
Inconvenience due to bulky container
Pressure to patients |
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| Pill count | Routine clinical practice | Primary nonadherence | Low cost
Simple
Can be used in various formulations
Highly accurate | Not for nondiscrete dosages or prn medications
Underestimation due to early refill
Arbitrary cutoff value
Unable to identify medication-taking pattern |
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| Measures involving clinician assessments and self-report | Routine clinical practice
Less suitable for research | It depends on the type of assessments and questionnaires used | Low cost
Easy to administer
Real-time feedback Available
Flexible to accommodate different conditions
Identify belief and barriers to adherence
Well-validated | Least reliable
Relatively poor sensitivity and specificity
Affected by communication skills of interviewers and questions in the questionnaire
Patient’s desirability can bias |
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