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Table 10 Results of studies assessing internal consistency of the instruments included in the review

From: Measuring carer quality of life in Duchenne muscular dystrophy: a systematic review of the reliability and validity of self-report instruments using COSMIN

Instrument N (DMD subsample) Mean (SD) Age (DMD subsample) % Female (DMD subsample) Country Cronbach’s α Rating of measurement property
Rating Quality of evidence
CWBS [35] 60 NR 41.7 India 0.92 + Moderate
DUKE [37] 126 43 (6.1) 57.4 Taiwan 0.81 + High
FAPGAR [37] 126 43 (6.1) 57.4 Taiwan 0.89 + High
FPQ [46]a 336 (246 DMD) 41.2 (6.2) for DMD carers 84.2 (83.3 DMD) Italy Ranged from 0.66 to 0.87 ? High
HADS (Anxiety) [32] 82 (71 DMD) 40.40 (6.98) 100 USA 0.87 + Moderate
HADS (Depression) [32] 82 (71 DMD) 40.40 (6.98) 100 USA 0.8 + Moderate
PAS [51] 205 at baseline (147 at year 1, 144 at year 2) 44 (8.7) 100 USA 0.96 + High
PPC [51] 205 at baseline (147 at year 1, 144 at year 2) 44 (8.7) 100 USA 0.79 + High
PSS [32] 82 (71 DMD) 40.40 (6.98) 100 USA 0.89 + Moderate
QRS [53] 36 43.04 (5.52) 69.44 Canada 0.86 + Low
SF-36 [32]a 82 (71 DMD) 40.40 (6.98) 100 USA Ranged from 0.76 to 0.88 + Moderate
SNQ (subscale A) [46] 336 (246 DMD) 41.2 (6.2) for DMD carers 84.2 (83.3 DMD) Italy 0.69 High
WAC-DBMD [51] 205 at baseline (147 at year 1, 144 at year 2) 44 (8.7) 100 USA 0.89 + High
ZBI (22 item) [60] 475 44 (NR) 81 UK, US 0.914 + High
ZBI (12 item) [51] 205 at baseline (147 at year 1, 144 at year 2) 44 (8.7) 100 USA 0.89 + High
  1. Citation next to the instrument is for the study assessing this measurement property
  2. NR, not reported
  3. aFPQ and SF-36 subscales were assessed separately, however Cronbach’s α was reported as a range across all scales