Psychometric properties of the Brief Mishel Uncertainty in illness scales for patients with advanced cancer and their family caregivers.

BACKGROUND

This study comprehensively examined the psychometric properties of the Brief Mishel Uncertainty in Illness Scale for patients (MUIS-P) managing advanced cancer and their caregivers (MUIS-Cg).

METHODS

The MUIS-P and MUIS-Cg scales were developed based on the Mishel Uncertainty in Illness Scale-Adult. We conducted a secondary analysis to test the acceptability, factor structure, reliability, and validity of the brief uncertainty scales for patients with advanced cancer (N = 484) and their caregivers (N = 484) using data from a randomized clinical trial.

RESULTS

The 9-item MUIS-P and MUIS-Cg show goodness of fit for a two-factor structure (unpredictability and ambiguity) with adequate to acceptable internal consistency (Cronbach's alpha 0.66-0.78 for patients and 0.70-0.72 for caregivers and McDonald's omega 0.72-0.84 for patients and 0.76-0.79 for caregivers). The MUIS-P and MUIS-Cg scores correlated with negative appraisals of illness/caregiving, hopelessness, and avoidant coping, demonstrating convergent validity. The discriminant validity of the MUIS-P and MUIS-Cg was evidenced by their significant correlations with self-efficacy and active coping. The baseline MUIS-P and MUIS-Cg scores were significantly associated with quality of life, hopelessness, depression, distress, and avoidant coping at the 3-month follow-up, indicating their strong predictive validity.

CONCLUSION

This study comprehensively evaluated the psychometric properties of the MUIS-P and MUIS-Cg, laying a foundation for their use in research and clinical practice among patients and caregivers managing demanding symptoms and care.