Symptom dimensions in people affected by long-term neurological conditions: a factor analysis of a patient-centred palliative care outcome symptom scale

Long-term neurological conditions (LTNCs) often cause debilitating symptoms. Better understanding of symptom dimensions in LTNCs is needed to support health professionals and improve care. This can be achieved by exploring the factor structure of a standardised measure of symptoms in LTNC patients. The symptom subscale of the Integrated Palliative Outcome Scale for LTNCs (IPOS Neuro-S24) comprises 24 items measuring symptom severity. Descriptive statistics and psychometric properties of the scale were assessed, followed by differential item functioning (DIF), exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Data from N = 238 patients were analysed. The mean IPOS Neuro S-24 score was 27.0 (possible range 0-96) and floor effects were found for 21 items. The scale had good internal consistency (Cronbach's alpha = 0.77). Weak evidence of DIF was found for nine items. All but one item (falls) loaded onto four factors with loadings > 0.3. The factors represented four clinically meaningful symptom dimensions: fatigue, motor symptoms, oral problems and non-motor symptoms. We identified a reliable four-factor structure of symptom experience in LTNC patients. The results suggest that symptom dimensions are common across LTNCs. The IPOS Neuro S-24 is an appropriate tool to measure symptoms in LTNC patients, which may improve care.