Table 2.

Feasibility measures and metrics

Feasibility measures		Feasibility metrics
1.	Mean number of days between the study’s first text message each month requesting text-messaged photographs and participants’ responses	At least 80% of responses within 5 days of our first text message request
2.	Mean number of reminder text messages required to elicit a response from the participant	A mean of 2 additional reminder text messages per participant for the duration of the study
3.	Mean frequency of nonresponse	A mean of 2 nonresponses per participant for the study duration
4.	Ability to extract the necessary information from images (mean number of attempts to receive clear pictures with the required information)	A mean of 2 additional text message attempts per participant for the duration of the study
5.	Mean length of time to recruit study participants	Mean duration of 3 months
6.	Percentage of participants retained until the end of the study	Text-messaged photographs of medication vials and vial contents at 6 months from over 80% of participants
7.	Mean number of mailed hair samples per participant	Receipt of 3 out of 4 mailed hair samples from at least 80% of participants
8.	Number of participants with whom we successfully conduct exit surveys and qualitative exit interviews	Conducting surveys with at least 80% of study participants and qualitative interviews with 30%