The purpose of this study is to conduct the Turkish cross-cultural adaptation, validity, and reliability study of the "Brief Inventory of Treatment Expectations in Chronic Pain" (BITEC) scale. Chronic pain is a complex, multidimensional experience that affects a significant portion of the adult population. Treatment expectations play a critical role in predicting clinical outcomes and directly influencing placebo/nocebo responses. While several tools exist to evaluate expectations, there is a lack of a concise, clinician-friendly, and Item Response Theory (IRT)-based instrument adapted for Turkish chronic pain populations. The BITEC is a 9-item scale that evaluates biological, psychological, and social/interactional expectation domains.

This methodological and cross-sectional study will be conducted with adult patients diagnosed with chronic pain for at least three months at Bingöl State Hospital. The study will be carried out in four consecutive stages: cross-cultural adaptation (forward and backward translation), comprehensibility pre-testing (with 30-40 volunteers), main data collection (with at least 200 participants), and statistical analyses. Data will be collected through printed forms and an online survey platform (Kobotoolbox), involving no clinical interventions. Participants will complete a sociodemographic information form, the Turkish version of the BITEC (BITEC-TR), the Treatment Expectations in Chronic Pain Scale (TEC-TR), the Pain Catastrophizing Scale (PCS), the Numerical Pain Rating Scale (NPRS), and the Hospital Anxiety and Depression Scale (HADS). Additionally, a subgroup of approximately 60 participants will recomplete the BITEC-TR 7-10 days after the initial session to evaluate test-retest reliability. Psychometric evaluation will include construct validity through exploratory and confirmatory factor analyses, and internal consistency and stability measurements.

This study is a methodological and cross-sectional research project aimed at the cultural adaptation and psychometric evaluation of the Brief Inventory of Treatment Expectations in Chronic Pain (BITEC) into Turkish. The study will be conducted at Bingöl University Faculty of Physical Therapy and Rehabilitation and Bingöl State Hospital Physical Medicine and Rehabilitation Outpatient Clinic. Data collection involves no clinical interventions and will be carried out using printed forms and an online survey platform (Kobotoolbox).

Procedure and Stages

The research will be executed in four consecutive stages:

Stage 1 - Cross-Cultural Adaptation: The BITEC will be adapted into Turkish following the ISPOR guidelines. Two independent native Turkish translators (one health professional, one linguist) will perform the forward translation. An expert panel will synthesize these translations into a consensus version. A native English speaker fluent in Turkish and blind to the original scale will perform the backward translation. The back-translated version will be compared with the original scale to eliminate semantic discrepancies.

Stage 2 - Comprehensibility Pre-testing: The provisional Turkish version will be administered to 30-40 volunteers diagnosed with chronic pain. Items will be rated on a scale from 0 (not comprehensible at all) to 10 (completely comprehensible). Items with a mean score below 8 will be revised.

Stage 3 - Main Data Collection: Eligible participants will be recruited to reach a target sample size of 200 to 250 individuals. Participants will complete a battery of assessments, including a sociodemographic and clinical information form, the BITEC-TR, the Treatment Expectations in Chronic Pain Scale (TEC-TR), the Pain Catastrophizing Scale (PCS), the Numerical Pain Rating Scale (NPRS), and the Hospital Anxiety and Depression Scale (HADS). For test-retest reliability, a subgroup of approximately 60 participants whose clinical status and treatment remain unchanged will recomplete the BITEC-TR 7-10 days after the initial assessment.

Stage 4 - Statistical Analysis: Data analysis will be performed using SPSS software (v.25). Normality will be assessed via the Shapiro-Wilk test. Construct validity will be examined using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA), reporting model fit indices such as CFI, NFI, RMSEA, and chi-square/df. Internal consistency will be evaluated using Cronbach's alpha, and test-retest reliability will be measured using the intra-class correlation coefficient (ICC). Measurement error will be calculated using the standard error of measurement (SEM) and minimal detectable change (MDC 95). Convergent, discriminant, and known-groups validities will be analyzed using Spearman correlation analyses based on pre-established hypotheses registered on the Open Science Framework (OSF). Ceiling and floor effects will also be evaluated.

Inclusion Criteria:

• Aged 18-70 years
• Having chronic pain for at least 3 months according to the International Association for the Study of Pain (IASP) criteria
• Diagnosed with any chronic pain condition (e.g., fibromyalgia, nociceptive pain, neuropathic pain, etc.)
• Being literate
• Currently receiving any medical treatment

Exclusion Criteria:

• Presence of cancer-related pain
• Diagnosis of acute pain
• Being unable to fill out the questionnaire due to a diagnosed cognitive impairment or psychiatric illness
• Presence of visual or motor disabilities that prevent completing the questionnaire

The study population consists of adult patients who have been diagnosed with any type of non-cancer chronic pain condition (such as fibromyalgia, nociceptive pain, neuropathic pain, osteoarthritis, rheumatoid arthritis, or chronic headache/migraine) for at least three months, are literate, and are currently undergoing medical treatment. The sample will be recruited from patients admitting to the Physical Medicine and Rehabilitation Outpatient Clinic at Bingöl State Hospital. Data will be collected through both printed forms in the clinical setting and an online survey platform (Kobotoolbox), ensuring representation of both outpatient clinic attendees and accessible chronic pain patient groups.

o ensure participant privacy and data confidentiality in accordance with national data protection laws (KVKK) and the approved ethical committee protocol, individual participant data will not be shared with third parties.