Reliability and validity of a single-item rating scale to monitor medication adherence for people living with HIV and lower health literacy

Abstract

Background:

Monitoring medication adherence in clinical and research settings may be especially challenging for people with lower literacy skills.

Objective:

The current study examined the measurement properties of a single-item rating scale (SIRS) for assessing medication adherence in a sample of 468 people living with HIV and lower health literacy skills.

Methods:

Participants completed two versions (computerized and telephone interview) of an SIRS as well as unannounced monthly pill counts. We also collected measures of common correlates of adherence and obtained participants' HIV RNA viral load from medical records.

Results:

Results indicated that the SIRS is time stable over one month (r = 0.46 to 0.52). There was limited evidence for modality effects between the computerized and phone administered SIRS. Associations with unannounced pill counts demonstrated concurrent and predictive validity of the SIRS, and criterion-related validity by associations with viral load. However, the SIRS also demonstrated inflated adherence estimates relative to unannounced pill counts and these discrepancies were greatest for persons of lower income and who reported alcohol use.

Conclusions:

A simple SIRS to monitor medication adherence may therefore be reliable and valid for use with people challenged by lower literacy skills in both clinical and research settings.

Keywords:

• HIV
• Health literacy
• Medication adherence