Reference values for the short forms of the Singapore Caregiver Quality of Life Scale

The 15- and 10-item short forms of the Singapore Caregiver Quality of Life Scale (SCQOLS-15 and SCQOLS-10) were recently developed as a quick assessment of caregiver quality of life. Reference values describing the distribution of the total and domain scores are available for the full-length version, but they are not yet available for the short forms. This study aimed to estimate the reference values for the short forms.

Data from a cross-sectional survey of 612 family caregivers of patients with advanced cancer in Singapore were fitted in quantile regression models. Percentiles were estimated by regressing the short forms' scores on caregiver characteristics. Classification by the reference values for the short forms and the full-length version were compared and agreement was evaluated.

The caregiver's role in caring for the patient and the patient's performance status were associated with the percentiles of the total scores and most domain scores (each Bonferroni-adjusted p-value, P_B, < 0.05). Higher-educated caregivers were categorized into higher percentiles according to the SCQOLS-15 and SCQOLS-10 total scores and the SCQOLS-15 Mental Well-being and Financial Well-being domain scores (each P_B < 0.05). Ethnicity was associated with the SCQOLS-15 Physical Well-being and Experience & Meaning domains (each P_B < 0.05). The percentiles for the short forms showed moderate to substantial agreement with those for the full-length version in terms of classifying caregivers into percentile intervals (quadratic-weighted Kappa = 0.72 to 0.92).

Reference values for the SCQOLS-15 and SCQOLS-10 were estimated in relation to caregiver characteristics to facilitate interpretation of the short form scores.