Psychometric Properties of a Lymphedema-specific Quality of Life Questionnaire in Lower Limb Lymphedema

Cross-cultural Validation of the French Version of the Lymphedema Functioning, Disability and Health Questionnaire for Lower Limb Lymphedema (Lymph-ICF-LL) and Responsiveness of the Dutch Version of the Lymph-ICF-LL

The goal of this observational study is to cross-validate the Lymphedema Functioning, Disability and Health Questionnaire for Lower Limb Lymphedema (Lymph-ICF-LL) in French and to investigate the responsiveness of the original Dutch Lymph-ICF-LL questionnaire in patients with lower limb lymphedema. The main questions it aims to answer are:

1. The reliability of the French Lymph-ICF-LL
2. The validity of the French Lymph-ICF-LL
3. The responsiveness of the original Dutch Lymph-ICF-LL

Participants are asked to complete questionnaires (Lymph-ICF-LL, Short Form-36, Global Perceived Effect Scale, questionnaire about the face and content validity) at two time points.

1. For reliability of the French Lymph-ICF-LL questionnaire:

   Native French speaking patients with stable lower limb lymphedema (LLL) (= in the maintenance phase of the treatment and no intensive multicomponent bandaging is required) are asked to complete the Lymph-ICF-LL questionnaire twice with an interval of 1-2 days in between.

   For the test-retest reliability following outcomes are calculated: Intraclass Correlation Coefficient(2,1), standard error of measurement and the smallest real difference.

   For internal consistency the Cronbach's alpha is calculated for the first completion of the questionnaire.

2. For the validity of the French Lymph-ICF-LL questionnaire, the construct validity, face and content validity are determined.

   2.1: For construct validity (=convergent and divergent validity), patients with stable lower limb lymphedema are asked to additionally complete the 36-item Short-Form Health survey (=health-related quality of life questionnaire) together with the first completion of the Lymph-ICF-LL questionnaire. For convergent validity, hypotheses are formulated about significant correlations between domains of the 36-item Short-Form Health survey (=SF-36) and domains of the Lymph-ICF-LL questionnaire which are expected to evaluate a similar construct: 'Physical functioning' of SF-36 and 'general tasks/household', 'mobility', 'life domains/social life' of the Lymph-ICF-LL; 'Role limitations due to physical health problems' of SF-36 and 'General tasks/household' of Lymph-ICF-LL; 'Bodily pain' of SF-36 and 'Physical function' of Lymph-ICF-LL; 'Social functioning' of SF-36 and 'Life domains/ social life' of Lymph-ICF-LL; 'Role limitations due to personal or emotional problems' of SF-36 and 'Mental function' of Lymph-ICF-LL; 'Mental health' of SF-36 and 'Mental function' of Lymph-ICF-LL. For divergent validity, hypotheses are formulated about weak or non-significant correlations between domains of the SF-36 and Lymph-ICF-LL: 'Physical functioning' of SF-36 and 'Mental function' of Lymph-ICF-LL; 'Role limitations due to personal or emotional problems' of SF-36 and 'Physical function' Lymph-ICF-LL; 'Mental health' of SF-36 and 'General tasks/household', 'Mobility', 'Life domains/social life' of Lymph-ICF-LL. These hypotheses were also used in previous published research of the validation of the original Dutch Lymph-ICF-LL questionnaire. Spearman rank correlation coefficients were calculated for this purpose.A correlation coefficient below .25 represent no to a little relationship, a value between .25 and .50 indicates a low to fair relationship, a value between .50 and .75 is interpreted as a moderate to good relationship and a value above or equal to .75 as a strong relationship.

   2.2 For face and content validity, patients with stable LLL are asked to complete an additional questionnaire about clarity and completeness of the Lymph-ICF-LL questionnaire: "Was each question of the Lymph-ICF-LL understandable? (yes/no)", "Was the scoring system clear? (yes/no)", "Were all complaints related to your lymphedema mentioned in the questionnaire? (yes/no)" and "Where there any questions of which you thought they were not relevant for lymphedema? (yes/no)". If patients answered 'no', they could clarify their answer in an open field.

3. For the responsiveness of the French and Dutch Lymph-ICF-LL, internal and external responsiveness is evaluated in patients with stable LLL and in patients who are treated in the intensive phase with multicomponent bandages. For internal responsiveness, patients with stable LLL have to complete the Lymph-ICF-LL questionnaire twice with an interval of 2 months. Patients treated in the intensive phase have to complete the questionnaire at the start of the intensive phase and 1 month after the end of the intensive phase. The Wilcoxon signed rank test is determined to evaluate if there is a significant difference between the total and subdomain scores of two completions in patients in the intensive phase and not in patients with LLL. For the external responsiveness, all patients are asked to complete the Global Perceived effect scale (GPE) together with the second completion of the Lymph-ICF-LL questionnaire. In this GPE questionnaire patient are asked to rate their perceived change in lymphedema-specific quality of life in general and concerning the subdomains of the Lymph-ICF-LL on a 7-point Likert-scale: 1=completely recovered, 2=much better, 3= a little better, 4= unchanged, 5= a little worse, 6= much worse, 7= worse than ever. Patients who give score 1 and 2 are labeled as responders, with score 3-5 as non-responders and with scere 6-7 as negative responders. The Wilcoxon signed rank test was determined between the total and subdomain scores in the positive, negative and non responder groups. Additionally spearman rank correlations coefficients are calculated between the change in total and subdomain scores and the GPE-score. The minimal clinically important difference are calculated with the anchor-based method: descriptive statistics of the change in total and subdomain scores of the Lymph-ICF-LL are determined in patients who indicated on the GPE that the lymphedema-specific quality of life was much improved or much worsened.

Inclusion Criteria:

• Primary or secondary lymphedema at the lower limb(s), i.e. a difference of ≥5% in volume between the two sides or a lymphoscintigraphy which shows at least 2 minor criteria or 1 major criterion or presence of indocyanine green (ICG) dermal backflow
• Unilateral/bilateral lymphedema
• Lymphedema stage 1, 2a, 2b or 3
• Lymphedema is present >3 months
• Chemotherapy and radiotherapy was finished >3 months ago
• Native French-speaking or Dutch-speaking for study about the French or Dutch Lymph-ICF-LL, respectively
• During the study patients are in the maintenance phase and not in the intensive phase (for the reliability/validity/responsiveness); patients receive intensive treatment in the hospital (for the responsiveness)
• Given informed consent to participate
• >18 years old

Exclusion Criteria:

• Not able to read or fully understand the French or Dutch language for study about the French or Dutch Lymph-ICF-LL, respectively
• For the reliability and validity and for part of the responsiveness: first treatment for lymphedema < 6 months ago and an intensive phase is planned or needed according to a specialized caregiver in treating lymphedema
• <18 years old
• Pregnant or breastfeeding women