Characteristics of Patients Declining INKA Trial Participation

Study Overview
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Brief Summary
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The objective of this study is to compare baseline characteristics of overweight knee OA patients accepting vs. declining enrolment in the INKA trial (NCT05172843) to explore if enrolled patients differ systematically from the declining participants with respect to both measured as well as unmeasured baseline characteristics.

Official Title
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Generalizability of Overweight Patients With Knee Osteoarthritis Awaiting Knee Surgery Accepting to Join a Weight Loss Randomized Trial: Protocol for a Cross-sectional Study Comparing Baseline Characteristics and Propensity of Patients Accepting/Declining Enrolment

Conditions
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Knee Osteoarthritis

Intervention / Treatment
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* Other: Acceptance of invitation to trial participation
* Other: Declining invitation to trial participation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18 or more A clinical and radiological diagnosis of knee OA BMI ≥ 30 kg/m2 Motivated for weight loss as by the provided program Signed informed consent. Exclusion Criteria: The scheduled surgery is for revision of an existing prosthesis Planned surgery for more than one knee within the observation period KA indication due to sequelae of fracture(s) Injection of medication or substances in the target knee within 3 months prior to participation Immuno-inflammatory arthritis as cause of the knee OA Current systemic treatment with glucocorticoids equivalent to > 7.5 mg of prednisolone/day Previous or planned obesity surgery Inability to understand or read Danish incl. instructions and questionnaires Any other condition or impairment that, in the opinion of the investigator (or his/her delegate), makes a potential participant unsuitable for participation or which obstruct participation.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| INKA participants<br>Individuals eligible and accepting participation in the INKA trial (NCT05172843) | Other: Acceptance of invitation to trial participation<br>* Individuals who are eligible for and accept participation in the INKA trial (NCT05172843)<br>|
| n-INKA participants<br>Individuals eligible and declining participation in the INKA trial (NCT05172843) | Other: Declining invitation to trial participation<br>* Individuals who are eligible for participation in the INKA trial (NCT05172843) but decline the invitation to participate<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Oxford knee score | The Oxford Knee Score (OKS) is a 12-item Patient Reported Outcome questionnaire developed specifically to assess the patient's perspective on the outcomes of knee arthroplasty (KA) with respect to combined pain and physical function. Standardized answer options are given (5 Likert boxes) and each question is assigned a score from 0 to 4. Thus, a total score is calculated that ranges from 0 and 48, with 48 indicating the best outcome. | Baseline | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Health outcome and quality of life survey (EQ-5D-5L) | EQ-5D-5L is a standardized patient-reported instrument for use as a measure of health outcome and quality of life. EQ-5D-5L is designed for self-completion by respondents and is ideally suited for use in surveys. The EQ-5D-5L consists of a descriptive system and the EQ Visual Analogue scale (EQ VAS). The descriptive system comprises 5 dimensions (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression). Standardized answer options are given (5 Likert boxes) and each question is assigned a score from 1 to 3. It is simple, taking only a few minutes to complete. Instructions to respondents are included in the questionnaire. The EQ-5D VAS records the respondent's self-rated health on a 20 cm vertical, visual analogue scale with endpoints labelled 'the best health you can imagine' and 'the worst health you can imagine'. | Baseline | 
| Analgesic use | At clinical outcome assessment visit, the participants will be interviewed by an investigator about their use of analgesics since last visit. The interview will be focused on intake of Paracetamol/acetaminophen NSAIDS Acetylic acids Opioids The use of these analgesics will be recorded as a 0-3 points Likert scale (0, never; 1, rarely; 2, 2-3 times per week; 3, daily or almost daily). | Baseline | 
| The Knee Injury and Osteoarthritis Outcome Score - 12 item short form (KOOS-12) | KOOS-12 provides scale scores for knee-specific Pain, Function and QOL, along with a summary measure of overall knee impact. Each item is scored from 0 to 4, with 0 representing no knee problems and 4 representing extreme knee problems. The separate KOOS-12 Pain, Function and QOL scale scores are calculated, in which item responses are summed. The KOOS-12 Summary knee impact score is calculated as the average of the KOOS-12 Pain, KOOS-12 Function and KOOS-12 QOL scale scores. A Summary impact score is not calculated if any of the three scale scores are missing. The KOOS-12 Summary impact score also ranges from 0 to 100, where 0 is the worst possible and 100 is the best possible score. | Baseline | 
| Patient's global assessment of impact of the knee in daily life (PGA) | The participant's assessment of the impact of their knee on everyday life is measured as the response to the question Taking into account all the activities you have during your daily life, your level of pain, and your functional impairment, how much does your [left/right] knee impact your daily life?. A 100 mm visual analogue scale (VAS) will be used as assessment instrument with anchors: 0 = No impact and 100 = Worst imaginable impact. | Baseline | 
| Body weight | The participants body weight is transferred from the medical records of their visit in the orthopaedic outpatient clinic. | Baseline | 
| Brief Illness perception questionnaire (B-IPQ) | B-IPQ is a generic 9-item questionnaire developed to rapidly assess the cognitive and emotional representations in a variety of illnesses. B-IPQ is a short version of the 84-item revised illness perception questionnaire (IPQ-R) (21). B-IPQ assesses perceptions on the following five dimensions: Identity, Cause, Timeline, Consequences and Cure-Control. Five of the items assess cognitive illness representations; two of the items assess emotional representations; and one item assesses illness comprehensibility. The 8 items are scored on a 0-3 Likert scale with descriptors (none or extreme) at either end. | Baseline |