Psychometric properties of the Functional Assessment of Cancer Therapy–Lung (FACT-L) scale to measure health-related quality of life

Purpose To validate the Functional Assessment of Cancer Therapy–Lung (FACT-L) scale and assess its psychometric properties in patients with lung cancer in Colombia. Methods The analysis included exploratory and confirmatory factor analysis, internal consistency (248 patients diagnosed with lung cancer), test–retest reliability (56 patients evaluated at two different time points), discriminant, convergent and divergent validity. Results Factor analysis revealed a two-dimensional structure within the lung cancer-specific subscale (LCS). Cronbach’s alpha was 0.91, ω McDonald 0.92 and Guttman’s λ2 0.92 for the FACT-L. Lin’s concordance correlation coefficient indicated test–retest reliability (0.8, 95% CI: 0.69–0.88) adequate for uses of the tool. Convergent validity assessed through Spearman’s rho correlation coefficient was 0.64 (95% CI: 0.56–0.71, p < 0.001). In divergent validity, the result was a rho − 0.432 (P = < 0.001); in discriminant validity was a rho of 0.141 ( P = 0.027). Conclusion Internal consistency analyses demonstrated strong inter-item correlations and high homogeneity. Discriminant, convergent, and divergent validity support the scale’s ability to distinguish between conceptually distinct constructs, and test–retest reliability confirmed temporal stability. The FACT-L scale is a valid and reliable instrument for assessing health-related quality of life in patients with lung cancer in the Colombian context.