Table 1.

Overview of participant assessment moments and outcome measurements

	Instrument	Pre randomisation	Baseline	12 weeks	24 weeks
Feasibility parameters
Interest of patients to be contacted about the study		x
Rate of eligible trial participants		x
Willingness of patients to consent to participate in PRINCE Primary
Willingness of participants to complete baseline measures before randomisation		x
Participants follow-up rates to questionnaires per group				x	x
Measures to identify suitable primary outcomes
Psychosocial functioning	WASAS		x	x	x
Physical symptoms	PHQ-15		x	x	x
Psychological distress	PHQ-9		x	x	x
Global outcome	CGI			x	x
Service use	CSRI and EQ-5D-5L		x		x
Potential mediators
Treatment outcome	CBRQ		x	x	x

CBRQ, Cognitive Behavioural Responses Questionnaire; CGI, Clinical Global Impression; CSRI, Client Service Receipt Inventory; EQ-5D-5L, EuroQol 5 Level; PHQ 9, Patient Health Questionnaire 9; PHQ-15, Patient Health Questionnaire 15; PRINCE Primary, Persistent Physical Symptoms Reduction Intervention: a System Change and Evaluation in Primary Care; WSAS, Work and Social Adjustment Scale.