Table 2.

Brief description of the validity properties assessed for the mHeart medication adherence electronic patient-reported outcome measures.

Validity properties	Descriptiona
Content validity	The interrater agreement among an expert panel was performed to assess the following three content validity aspects. The expert panel comprised 14 health professionals, including 3 nurses, 7 cardiologists, and 4 clinical pharmacists. The suitability of the questionnaires proposed for inclusion in the mHeart app. The discussion was verbal, and voting was by hand. The suitability of the ePROMsb compared with the traditional in-clinic version. After written records were taken, a verbal discussion was held. The suitability of the six medication difficulties added to the electronic version of the Haynes-Sacket questionnaire. After written records were taken, a verbal discussion was held.
Convergent and discriminant validity	Convergent and discriminant validity were assessed using the following aspects: The correlation between the ePROM rates and a standard questionnaire was assessed. The complementarity of the adherence to medication domains of the ePROMs included in the mHeart system was measured.
Reliability (reproducibility)	Reliability and reproducibility were assessed using two methods with different purposes: The equivalent forms reliability method was used to assess the adequate association between the ePROMs scores and the in-clinic scores. With this aim, the PROMs were assessed in the same group of patients and on the same day. The test-retest reliability method was used to assess the stability of the ePROM scores during a short time period (7 days) in clinically stable patients.
Responsiveness (sensitivity to change)	Change over time in medication adherence was measured by the difference in ePROM scores while a theory-based intervention program was performed. A 1-month interval was considered adequate to measure the validity of an indirect smartphone measure [51,52].
Interpretability	Three aspects of the interpretability property were analyzed and discussed: The interpretation of the ePROM scores. The meaningful change detected. The scores obtained versus those published by other authors.
Respondent and administrative burden	Several criteriaa were assessed regarding the time, effort, and other criteria of the ePROMs, depending on the respondents’ and administrative points of view.

^aFull details on validity properties assessed are provided in Multimedia Appendix 7.

^bePROM: electronic patient-reported outcome measure.