Development and Validation of the Breast Cancer Scale QLICP-BR V2.0 Based on Classical Test Theory and Generalizability Theory

Objective The aim of this study was to develop and validate the breast cancer scale among the system of quality-of-life instruments for cancer patients (QLICP-BR V2.0). Methods Programmed decision procedures and theories on instrument development were applied to develop QLICP-BR V2.0. A total of 246 breast cancer inpatients were investigated using QLICP-BR V2.0 from hospital admission until discharge. The reliability, validity, and responsiveness of the QLICP-BR V2.0 scale were evaluated by using the classical test theory combined with the generalizability theory (GT), including correlation analysis, multi-trait scaling analysis, factor analyses, t-tests, and also multivariate generalizability theory analysis. Results The test–retest reliability of the total scale is 0.79, the Cronbach coefficient is 0.85, and the intra-class correlations coefficient is 0.88. The item–domain correlation analysis showed that the correlation coefficient between items and their own domain is greater than that with other domains except of item GSO4. The exploratory factor analysis showed that three principal components are obtained in the specific module. The outcome of the factor analysis coincides substantially with our theoretical conception. The score difference of each domain of the scale and the total scale before and after treatment is statistically significant (P < 0.05), with the standardized response mean of the total scale being 0.61. According to GT, the generalization coefficient of the scores in the 5 domains is between 0.626 and 0.768, and the reliability index is between 0.557 and 0.695. Conclusion QLICP-BR V2.0 exhibited reasonable degrees of validity, reliability, and responsiveness according to classical test and the generalizability theory. The number of items in the scale is appropriate.