Evaluation of patient-relevant outcomes of lymphedema and lipedema treatment: development and validation of a new benefit tool

OBJECTIVES: Patient-relevant treatment benefit is traditionally measured with health-related quality of life (HRQoL) instruments. The Patient Benefit Index (PBI) methodology allows for a more direct measurement, with the patients rating both importance and achievement of treatment goals. Here, we developed and validated a PBI version specific for the assessment of benefit in lymphedema and lipedema treatment (PBI-L). METHODS: The development included five steps: (1) open item collection; (2) consensus of items in a multidisciplinary expert panel; (3) application of the German PBI-L in a cross-sectional study (n = 301); (4) translation into English; (5) application of the English PBI-L in a randomized clinical trial (n = 82). Subscales were developed using factor analysis. Construct validity was analyzed by correlating PBI-L and convergent criteria such as HRQoL and quality of care. To test for responsiveness, the association to change in HRQoL measures was computed. RESULTS: Floor and ceiling effects were low. There were few missing values. Two well-interpretable subscales were found with Cronbach's alpha >0.8 each. Global and subscale scores correlated with convergent criteria and with change in disease-specific HRQoL, but not with change in generic HRQoL. CONCLUSIONS: The PBI-L is an internally consistent, valid, and responsive instrument for the assessment of patient-relevant benefit of edema treatment.