Measurement of fatigue: Comparison of the reliability and validity of single-item and short measures to a comprehensive measure

Background Evidence is needed on the clinicometric properties of single-item or short measures as alternatives to comprehensive measures. Objectives We examined whether two single-item fatigue measures (i.e., Likert scale, numeric rating scale) or a short fatigue measure were comparable to a comprehensive measure in reliability (i.e., internal consistency and test–retest reliability) and validity (i.e., convergent, concurrent, and predictive validity) in Korean young adults. Methods For this quantitative study, we selected the Functional Assessment of Chronic Illness Therapy–Fatigue for the comprehensive measure and the Profile of Mood States–Brief, Fatigue subscale for the short measure; and constructed two single-item measures. A total of 368 students from four nursing colleges in South Korea participated. We used Cronbach's alpha and item-total correlation for internal consistency reliability and intraclass correlation coefficient for test–retest reliability. We assessed Pearson's correlation with a comprehensive measure for convergent validity, with perceived stress level and sleep quality for concurrent validity and the receiver operating characteristic curve for predictive validity. Results The short measure was comparable to the comprehensive measure in internal consistency reliability (Cronbach's alpha = 0.81 vs. 0.88); test–retest reliability (intraclass correlation coefficient = 0.66 vs. 0.61); convergent validity (r with comprehensive measure = 0.79); concurrent validity (r with perceived stress = 0.55, r with sleep quality = 0.39) and predictive validity (area under curve = 0.88). Single-item measures were not comparable to the comprehensive measure. Conclusions A short fatigue measure exhibited similar levels of reliability and validity to the comprehensive measure in Korean young adults.