Validation of the Dutch version of the Mishel Uncertainty in Illness Scale-C in patients with advanced cancer receiving systemic treatment

Background: An emerging group of patients with advanced cancer receiving systemic treatment lives long term with ongoing uncertainty, but no valid measure of uncertainty was available for this group. Our aims were to translate the Mishel Uncertainty in Illness Scale-Community (MUIS-C) into the Dutch language and evaluate its psychometric properties in patients with advanced cancer receiving systemic treatment. Methods: Patients (N = 111) with diverse advanced cancer diagnoses and treatments (53% male, mean age 66 years) completed the MUIS-C, which was translated into the Dutch language using a forward-backward translation procedure. Floor and ceiling effects, structural validity, internal consistency, and construct validity were evaluated. Results: No floor and ceiling effects for the MUIS-C were found. Exploratory factor analysis revealed two factors (lack of clarity, unpredictability). Internal consistency was adequate (Cronbach's α = 0.82). All a priori hypotheses regarding convergent and divergent validity were confirmed and supported construct validity. Conclusions: Results suggest that the Dutch MUIS-C is a valid and reliable measure for assessing illness uncertainty in patients with advanced cancer and support its use in future studies among patients with advanced cancer receiving systemic treatment.