Abstract
Assessment of psychological distress by patient report is necessary to meet patients' needs throughout the cancer journey. We have previously developed an item bank to assess psychological distress but not evaluated it for cancer survivors. Our first aim in this study was to test whether we could extend our item bank to include cancer survivors. The second aim was to examine whether the item bank could assess positive affect as a single construct alongside negative psychological symptoms. Methods Responses from 1315 cancer survivors to the Hospital Anxiety and Depression Scale (HADS) and the Positive and Negative Affect Scale (PANAS) were considered for inclusion in a pre-existing item bank created from a heterogeneous sample of 4914 cancer patients. Differential item functioning (DIF) was used to assess whether HADS responses drawn from the two samples were equivalent. Common-item equating was used to anchor the shared (HADS) items, whilst the PANAS items were added. Item fit was evaluated at each stage, and misfitting items were removed. Unidimensionality was assessed with a principal components factor analysis. Results The DIF analysis did not reveal any differences between the HADS item locations from the two samples. Three misfitting PANAS items were removed, resulting in a final unidimensional bank of 80 items with good internal reliability (α = 0.85). Conclusion The new item bank is valid for use across the cancer journey, including cancer survivors, and modestly improves the assessment of all levels of psychological distress and positive psychological function.