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Table 1 Measures and Scales

From: Caregiving in ALS – a mixed methods approach to the study of Burden

Psychological Distress - Depression and Anxiety.

 The Hospital Anxiety and Depression Scale (HADS) [18] is composed of two 7-item subscales, with a four point ordinal response format (0–3), assessing Anxiety (HADS-A) and Depression (HADS-D). Possible scores from 0 to 21 on each subscale [23].

 A score of 0–7 in either subscale indicates a normal range, 8 to 10 a possible clinical level, and 11 or over is indicative of probable clinical level [23]. The use of a summed HADS total score (HADS-T) is seen as an adequate estimate of general psychological distress [39].

Quality of Life

 The McGill Quality of Life Single Item Scale (MQol SIS) [19], is a single item numerical rating scale (0–10) constructed to measure self-reported quality of life (QoL). The respondent is asked to consider all parts of his/her life: physical, emotional, social, spiritual, and financial and to indicate whether over the past two days their quality of life has been - 0 ‘Very Bad’ to 10 ‘Excellent’. Higher scores are indicative of greater subjective wellbeing and quality of life.

Caregiver Burden

 The Zarit Burden Interview (ZBI) [17] is a widely used instrument for measuring subjectively assessed caregiver burden. The ZBI is composed of 22 items rated on a 0–4 scale, with a maximum score of 88. The global score is the sum of all item scores, higher scores indicate greater caregiver burden.

 ZBI cut-off scores which range from 24–26 are useful in identifying caregivers at risk of depression and in need of further assessment and intervention [26]; caregivers with a score of ≥24 are categorically defined as being in a clinically ‘high burden’ group, as this methodology has accurately predicted determinants of caregiver burden in ALS [13].

Burden dimensions:

 Role Strain comprises 9 ZBI items with a possible range of 0–36;

 Personal Strain comprises 10 ZBI items with a possible range of 0–40;

 Guilt comprises 2 ZBI items with a possible range of 0–8.

 The ZBI item 22 which asks “Overall, how burdened do you feel in caring for this person?” was not included in this analysis. This item provides a global estimate of burden and loaded high on both factors Personal and Role Strain [31].