Table 1 Questionnaires used for screening and evaluation purposes at intake, Week 5 (mid-trajectory evaluation), and Week 10 (end evaluation)

General CIR questionnaire

Not applicable

Records general socio-demographic characteristics, as well as symptom-related information, co-morbidity and medication levels

The follow-up questionnaire in Weeks 5 and 10 again records the presence and strength of the symptoms, as well as the perceived effect of the treatment on pain, coping and limitations in daily functioning. In Week 10, work ability, satisfaction with the treatment and potential side effects are additionally recorded

Symptom Checklist 90^a

SCL-90

Measures to what degree the patient suffers from 90 different physical and psychological symptoms. [16]

Pain Self-Efficacy Questionnaire

PSEQ

Measures how confident the patient is that he/she will be able to perform daily tasks despite being in pain. [17]

Psychological Inflexibility in Pain Scale

PIPS

Measures psychological inflexibility (avoidance of pain and cognitive fusion with pain). [18]

Hospital Anxiety and Depression Scale

HADS

Measures feelings of fear and depression, without looking at physical complaints. [19]

Brief Illness Perception Questionnaire

BIPQ (Dutch: IPQ-K)

Measures the cognitive and emotional representation of illness in a patient. [20]

Pain Catastrophizing Scale

PCS

Measures degree of catastrophising. [21]

Checklist Individual Strength

CIS

Measures subjective tiredness. [22]

Pain Disability Index

PDI

Measures to what degree pain prevents the patient from participating in daily activities. [23]

Twelve-Item Short Form Health Survey

SF-12

Measures physical and mental functioning. [24]

Patient-Specific Complaint

PSC (Dutch: PSK)

Measures a patient’s functional status by asking, for three examples of self-selected daily activities, to what degree the patient is limited in these activities by his/her pain complaints. [25]

6 min walk test^a

Not applicable

Measures physical performance by recording the distance in metres the patient can walk in 6 minutes, resting and maximal heart rate, and the level of exertion at the end of the test

5 times sit to stand test^a

Not applicable

Measures physical performance by recording the time in seconds needed for a patient to stand up five times from a chair without arms as fast as possible (twice)