Immediate test-retest reliabilities of intention to quit smoking measures in current adult smokers

Background: The Stages of Change (SOC) measure and Motivation To Stop Scale (MTSS) are regularly used to capture current smokers’ intention to quit (ITQ) cigarette smoking. They were shown to have comparable performances in construct and predictive validity, but their immediate test-retest reliabilities have not been investigated. In this randomized online two-arm study, we examined the immediate test-retest reliability of both SOC and MTSS measures.

Methods: Adult current smokers were randomized to complete an electronic version of either the SOC or MTSS, which was filled out before and after completing a filler task. Test-retest reliability was assessed with Cohen’s kappa coefficients. Intraclass correlation coefficients (ICC) were calculated as an index of reliability for the MTSS, when expressed as a continuous variable.

Results: A total of 722 participants were included in the analyses, with 311 and 411 completing the SOC and MTSS, respectively. The two measures showed high reliability; Cohen’s kappa coefficients of the ITQ measures ranged from 0.73 to 0.95, corresponding to substantial agreement up to “almost perfect” or “perfect” agreement. The ICC coefficient for the MTSS was 0.86, corresponding to excellent agreement.

Conclusions: Both measures have good test-retest reliability over a brief time interval. Instrument selection should be driven by the specific study objective and whether the investigation is intended to measure ITQ specifically or more broadly.