Evidence of the reliability and validity of the carer QOL instruments
| Reliability | Validity | |||||
|---|---|---|---|---|---|---|
| Carer QOL instrument | Author(s) | Internal consistency | Test–retest | Measurement error | Content validity | Construct validity |
| HDQoL-C | Aubeeluck and Buchanan17 | Not provided for total scale. Subscale α: 0.80, 0.84, 0.89 | Test–retest (N=10) over 2 weeks. Pearson correlation: 0.78, 0.86, 0.90 for subscales | Not assessed | Two experts in the field of QOL and two experts in the field of HD commented on item content | Convergent validity: positive correlations of HDQoL-C subscales with WHOQOL-BREF, Satisfaction with Life Scale, and Perceived Health Visual Analogue Scale |
| HDQoL-C-SF | Aubeeluck et al18 | Not provided for total scale. Subscale α: 0.88, 0.80 | Not assessed | Not assessed | Not assessed | Known groups analyses showed that HDQoL-C-SF scores were higher (better carer QOL) for carers of patients in the low disease severity group compared with the moderate and high severity groups |
| CAREQOL-MS | Benito-Leon et al19 | Not provided for total scale. Subscale α: 0.90, 0.85, 0.81, 0.78, 0.75 | Test–retest (N=276) over 2 weeks. ICC for total scale score=0.96 and ranged from 0.75 to 0.95 for subscales. Cohen's κ ranged from 0.46 to 0.93. One item had κ<0.60 and 15 items had κ≥0.80. | SE of measurement ranged from 0.91 to 2.43 across the five subscales over 2 weeks time interval. | Item content analysed by MS experts. Focus groups of MS carers and patients discussed item pool. Items rated for clarity and meaning by MS experts and a separate carer sample | Convergent validity: positive correlations of CAREQOL-MS subscales with Zarit Burden Interview. Moderate-to-high negative correlations of CAREQOL-MS subscales with physical and mental components of SF-36 |
| ACQLI | Doward20 | α ranged between 0.87 and 0.95 across the UK, France, Germany, Italy and Spain for times 1 and 2 administrations of the ACQLI. | Test–retest over 2 weeks. Spearman correlations were 0.93, 0.92, 0.95, 0.94, 0.90 for UK, France, Germany, Italy and Spain, respectively. Based on very small N per country | Not assessed | Field test of items with samples of carers. States that carers found the ACQLI to be understandable, acceptable and relevant across all countries | Convergent validity: positive spearman correlations of ACQLI with General Well-being Index in UK and Italy. Known groups analysis demonstrated that the ACQLI can distinguish between carers based on their current health status. |
| PDQ-Carer | Jenkinson et al21 | Not provided for total scale. Subscale α: 0.92, 0.87, 0.86, 0.83 | Not assessed | Not assessed | Very limited assessment of content validity. Items were evaluated by focus groups of researchers and a pilot sample of carers. | Convergent validity: moderate-to-high negative correlations of PDQ-Carer subscales with physical and mental components of SF-36 |
| PDQ-Carer-SI | Morley et al23 | α=0.94 | Not assessed | Not assessed | Not assessed | Convergent validity: moderate-to-high negative correlations of PDQ-Carer-SI score with physical and mental components of SF-36 |
| Parkinsonism Carers QoL (PQoL Carers) | Pillas et al22 | α=0.96 | Not assessed | Not assessed | Very limited assessment of content validity. The questionnaire was pilot tested in a small group of carers | Convergent validity: Subscales of PQoL Carers correlated with Caregiver Burden Inventory, Hospital Anxiety and Depression Scale and the EQ-5D. ANOVA revealed that PQoL Carers scores differentiate between carers based on their current health status. |
| Caregiver Quality Of Life (CGQOL) | Vickrey et al6 | Not provided for total scale. Subscale α: 0.88, 0.93, 0.78, 0.83, 0.86, 0.86, 0.82, 0.94, 0.92, 0.89 | Test-retest (N=71) between 11 and 63 days following first administration (75% within 21 days). ICC ranged from 0.53 to 0.89, exceeding 0.70 for 6 of the 10 subscales | Not assessed | Not assessed | Convergent validity: Regression and correlation analyses of CGQOL subscales with a range of patient and carer characteristics (e.g. number of hours spent caregiving, duration of being a carer) |
ACQLI, Alzheimer's Carers Quality of Life Instrument; CGQOL, Caregiver Quality Of Life; HD, Huntington's disease; HDQoL-C, Huntington's disease quality-of-life battery for carers; HDQoL-C-SF, Huntington's disease quality-of-life battery for carers short form; ICC, intraclass correlation coefficient; MS, multiple sclerosis; PDQ-Carer-SI, Parkinson Disease Questionnaire for Carers Summary Index; PQoL Carers, Parkinsonism Carers QoL; QOL, quality of life.