Table 1 Summary of approaches to measuring adherence to different contraceptive methods
Contraceptive method | Measurement approach | Advantages | Disadvantages |
|---|---|---|---|
Oral Contraceptive | Direct observation (clinician observes ingestion of pill) | Accurate and equates to ingestion | Impractical |
Self-reports (self-completed or interview administered questionnaire) | Simple, inexpensive and easy to administer. | Requires training for administrators. Subject to recall and social desirability bias. | |
Clinic / pharmacy records | Can help to correct poor recall. Simple, inexpensive and objective. Usually easy to obtain data. Can measure at more than one point in time. | Does not equate to ingestion and requires a closed pharmacy system | |
Pill counts (individual pill or pill pack counts) | Objective; quantifiable and easy to perform. | However, easily altered by participant (e.g. pill dumping), cannot assess timing of use | |
Electronic Monitoring Devices | Objective, precise, tracks patterns of use over time. | Potentially expensive and may require return visits to download data. Participants may not adhere to using device, intervention might improve use of device rather than pill-taking behaviour. | |
Blood hepatic binding globulin levels (Corticosteroid Binding Globulin, Thyroxine Binding Globulin, Lutenizing Hormone and Sex Hormone Binding Globulin) | Objective. Can distinguish between consistent use and non-use (Corticosteroid Binding Globulin and Thyroxine Binding Globulin more discriminating). Inexpensive compared to measuring contraceptive steroid level | Requires specialist laboratory. Can’t distinguish between consistent and inconsistent users | |
Blood contraceptive steroid level (e.g. Levonorgestrel or Ethinylestradiol) | Objective, indicates indigestion. | Difficult test, expensive therefore limited potential for replication in other studies, requires a blood test, will not distinguish consistent from inconsistent users | |
IUD / implant | Self-report | Simple, inexpensive and easy to administer. | Subject to recall bias and social desirability bias |
Clinical examination or ultrasound | Simple, inexpensive and easy to administer. | Intrusive, has to be performed in clinic setting, requires skilled personnel/ equipment | |
Clinic or client record | Objective | Requires a closed pharmacy system. Self-held record can get lost | |
Injection | Self-report | Simple, inexpensive and easy to administer. | Subject to recall bias and social desirability bias. |
Clinic or clinic record | Objective and indicates current use | Requires a closed pharmacy system. Self-held record can get lost |