Development of the Japanese Core Outcome Measures Index (COMI): cross-cultural adaptation and psychometric validation

Table 1 Reference questionnaires

Questionnaire	Content	Scale	Item number	Score range	COMI domains expected to correlate strongly
EQ-5D [18]	General health status				Summary, QOL
The descriptive system	Mobility, self-care, usual activities, pain/discomfort, and anxiety/depression	3-point Likert	5	−0.111–1.000^a
EQ-VAS		VAS	1	0–100^b
RDQ [19]	Physical disability due to low back pain	Dichotomous (yes or no)	24	0–24^c	Summary, Function, Disability
SF-8 [20]	General health-related quality of life	5- or 6-point Likert	8
PCS				5.32–70.69^d	Summary, Pain, Function, Symptom-specific well-being, QOL
MCS				10.11–74.51^d	Symptom-specific well-being, QOL
STarT [21]	Potentially modifiable prognostic indicators Five questions related to the psychological factors constitute the sub-score	5-point Likert and Dichotomous (agree or disagree)	9	0–9^e	Summary, Pain, Function, Disability

^aCalculated using the value set for the Japanese population [34]. The score of 1 denotes “full health” and 0 “death”
^bThe score of 0 indicates worst imaginable health state and 100 best possible health state
^cA higher score indicates greater disability
^dCalculated based on a norm-based scoring method given in the instrument guidelines [21]. A higher score indicates better health
^eA total score of 0–3 indicates low prognostic risk; a total score of ≥4 with sub score of ≤3, medium prognostic risk; sub score of ≥4, high prognostic risk
EQ-5D: the EuroQol 5 Dimension; VAS: visual analogue scale; RDQ: Roland Morris Disability Questionnaire; SF-8: Short Form 8™ Health Survey; PCS: physical component summary; MCS: mental component summary; STarT: the Keele STarT Back Screening Tool

ISSN: 1471-2474