Reliability and Validity of Measures for Investigating the Determinants of Health Behaviors Among Women With a History of Gestational Diabetes

Abstract

Aim. Assisting women with a history of gestational diabetes mellitus (GDM) to adopt healthy lifestyles is a priority for diabetes prevention. The aim of this study was to develop and evaluate measures that can be used to assess the efficacy of behavior change interventions in this group. Method. Measures of psychosocial influences on physical activity and diet were derived from formative research and examination of established instruments. Item reduction by principal components analysis was undertaken following telephone survey administration to 160 women with recent GDM, and the internal reliability and construct validity of the derived scales were assessed. Test–retest reliability was assessed in another sample of 97 women. Results. Scales with acceptable internal reliability were developed for physical activity outcome expectancies (α = .82), perceived barriers (α = .75), encouragement (α = .76) and self-efficacy (α = .82), weight control attitudes (α = .90), and diabetes-related fear (α = .70). Construct validity in relation to physical activity participation was found for the encouragement and self-efficacy scales. The weight control attitudes scale showed construct validity in relation to fruit and vegetable intake. The test–retest reliability of most scales was moderate to good (weighted κ = 0.55-0.69). Conclusion. Reliable and valid measures relevant to the psychosocial needs of women with GDM have been developed with a multiethnic population. These will assist future evidence generation, particularly in relation to the adoption of physical activity, which has been a challenging area of lifestyle intervention to date.