Evaluation of the palliative symptom burden score (PSBS) in a specialised palliative care unit of a university medical centre - a longitudinal study

BACKGROUND: The implementation of standardised, valid and reliable measurements in palliative care is subject to practical and methodological challenges. One aspect of ongoing discussion is the value of systematic proxy-based assessment of symptom burden in palliative care. In 2011, an expert-developed proxy-based instrument for the assessment of symptom burden in palliative patients, the Palliative Symptom Burden Score (PSBS), was implemented at the Specialised Palliative Care Unit of the University Medical Centre in Dusseldorf, Germany. The present study investigated its feasibility, acceptance and psychometric properties. METHODS: The PSBS was rated by nursing staff three times a day over 5 years (N = 820 patients). Feasibility and nurses’ acceptance of PSBS were analysed. Structural validity was investigated by principal component analysis. Construct validity was examined via cross-validation with the Hospice and Palliative Care Evaluation checklist. Discriminative validity of the PSBS was analysed by means of Kruskal-Wallis test of patients’ performance score. Reliability of the PSBS was evaluated by internal consistency analysis, test-retest and split-half-reliability. Inter-rater reliability was investigated by observer agreement of nurses’ ratings of symptom burden within a day. Sensitivity to change was analysed by Wilcoxon test with repeated measures of the PSBS before and after palliative complex treatment. RESULTS: A high degree of acceptance and the feasibility of a high-frequency proxy-based symptom burden assessment approach were demonstrated. There were low rates of missing values and no indications of the adoption of prior ratings. PSBS in its present form demonstrates good structural and construct validity (r(s) = .27–.79, p’s < .001) and high sensitivity to changes in symptom burden (p’s < .01, except sweating), but unsatisfactory reliability (α = .41–.67; test-retest: r(s =) .30–.88; p’s < .001; split-half: r(s) = .69; p < .001; inter-rater: n.s.). CONCLUSIONS: The study presents a framework for the post hoc validation of an already existing documentation tool in palliative care. This study supports the notion that PSBS might not be reflective of an overall construct and will therefore require further development and critical comparison to other already established symptom burden instruments in palliative care.