RESUMEN
BACKGROUND: The aim of this study is to validate the Basic Documentation for Psycho-Oncology Short Form (PO-Bado SF), a six item interview-based expert rating scale for distress screening in cancer patients. METHODS: Using a heterogeneous multicenter study sample (n = 1551), we examined validity, reliability, and dimensionality of the PO-Bado SF. The Hospital Anxiety and Depression Scale (HADS), the Distress Thermometer, the Questionnaire on Stress in Cancer, and the Patient Health Questionnaire were used to investigate convergent validity. Confirmatory factor analysis was applied to address unidimensionality. An optimal cutoff point was determined by ROC analysis and the maximum of Youden's index. An additional study with n = 41 audio recorded PO-Bado SF interviews was carried out to assess inter-rater reliability. RESULTS: Mean age of the study sample was 64.0 (SD = 12.0), 42% were women. About 24% of the patients suffered from metastases. The one-factor solution was confirmed; internal consistency of the PO-Bado SF was high (α = 0.84). The PO-Bado SF total score correlated significantly with all psychosocial measures, the highest correlation was with the HADS total score (r = 0.64). Patients with severe disease conditions (metastases, psychological/psychiatric treatment in the past, low performance status) received higher distress ratings (p < 0.001). Using HADS total score (>13) as external criterion, an optimal PO-Bado SF cutoff score of >9 emerged (sensitivity 0.75; specificity 0.82). Inter-rater reliability was satisfactory for each of the six items (intra class correlation of 0.75 to 0.85). CONCLUSIONS: The PO-Bado SF is a short, reliable and valid expert rating scale to identify distressed cancer patients.