Validity and test-retest reliability of the self-completion adult social care outcomes toolkit (ASCOT-SCT4) with adults with long-term physical, sensory and mental health conditions in England

BACKGROUND The Adult Social Care Outcomes Toolkit (ASCOT-SCT4) is a multi-attribute utility index designed for the evaluation of long-term social care services. The measure comprises eight attributes that capture aspects of social care-related quality of life. The instrument has previously been validated with a sample of older adults who used home care services in England. This paper aims to demonstrate the instrument's test-retest reliability and provide evidence for its validity in a diverse sample of adults who use publicly-funded, community-based social care in England. METHODS A survey of 770 social care service users was conducted in England. A subsample of 100 services users participated in a follow-up interview between 7 and 21 days after baseline. Spearman rank correlation coefficients between the ASCOT-SCT4 index score and the EQ-5D-3 L, the ICECAP-A or ICECAP-O and overall quality of life were used to assess convergent validity. Data on variables hypothesised to be related to the ASCOT-SCT4 index score, as well as rating of individual attributes, were also collected. Hypothesised relationships were tested using one-way ANOVA or Fisher's exact test. Test-retest reliability was assessed using the intra-class correlation coefficient for the ASCOT-SCT4 index score at baseline and follow-up. RESULTS There were moderate to strong correlations between the ASCOT-SCT4 index and EQ-5D-3 L, the ICECAP-A or ICECAP-O, and overall quality of life (all correlations ≥ 0.3). The construct validity was further supported by statistically significant hypothesised relationships between the ASCOT-SCT4 index and individual characteristics in univariate and multivariate analysis. There was also further evidence for the construct validity for the revised Food and drink and Dignity items. The test-retest reliability was considered to be good (ICC = 0.783; 95% CI: 0.678-0.857). CONCLUSIONS The ASCOT-SCT4 index has good test-retest reliability for adults with physical or sensory disabilities who use social care services. The index score and the attributes appear to be valid for adults receiving social care for support reasons connected to underlying mental health problems, and physical or sensory disabilities. Further reliability testing with a wider sample of social care users is warranted, as is further exploration of the relationship between the ASCOT-SCT4, ICECAP-A/O and EQ-5D-3 L indices.