Single-item vs multiple-item measures of stage of change in compliance with prescribed medications.

The Stage of Change construct from the Transtheoretical Model of behavioral change has been widely utilized in the assessment of various health behaviors. The majority of these tests measure the Stage of Change construct using the single-item, multiple-choice format. This study validated the use of a single-item measure in measuring readiness to comply with taking a prescribed medication. A sample of 161 subjects tested the multiple-item Stage of Change measure, then a refined multiple-item survey was tested with 59 subjects. With the latter survey, discriminating subjects at the differing stages of change dimensions was difficult. A correlation of .91 was found for stage classifications between ratings on the single-item and multipleitem scales. The use of the single-item measure seems reasonable when assessing stage of change in compliance with prescribed medication.