Clinical relevance of single item quality of life indicators in cancer clinical trials

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Abstract
We investigated the hypothesis that global single-item quality-of-life indicators are less precise for specific treatment effects (discriminant validity) than multi-item scales but similarly efficient for overall treatment comparisons and changes over time (responsiveness) because they reflect the summation of the individual meaning and importance of various factors. Linear analogue self-assessment (LASA) indicators for physical well-being, mood and coping were compared with the Hospital Anxiety and Depression Scale (HAD), the Mood Adjective Check List (MACL) and the emotional behaviour and social interaction scales of the Sickness Impact Profile (SIP) in 84 patients with early breast cancer receiving adjuvant therapy. Discriminant validity was investigated by multitrait-multimethod correlation, responsiveness by standardized response mean (SRM). Discriminant validity of the indicators was present at baseline but less under treatment. Responsiveness was demonstrated by the expected pattern among treatments (P = 0.008). In patients without chemotherapy, the SRMs indicated moderate (0.5-0.8) to large (>0.8) improvements in physical well-being (0.70), coping (0.92), HAD anxiety (0.89) and depression (1.19), and MACL mental well-being (0.68). In patients with chemotherapy for the first 3 months, small but clinically significant improvements (>).2) included mood (0.38), coping (0.41), HAD axiety (0.31) and MACL mental well-being (0.35). Patients with 6 months chemotherapy showed no changes. The indicators also reflected mood disorders (HAD) and marked psychosocial dysfunction (SIP) at baseline and under treatment according to pre-defined cut-off levels. Global indicators were confirmed to be efficient for evaluating treatments overall and changes over time. The lower reliability of single as opposed to multi-item scales affects primarily their discriminant validity. This is less decisive in large sample sizes.