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

Abstract

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). 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. 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. The PBI-L is an internally consistent, valid, and responsive instrument for the assessment of patient-relevant benefit of edema treatment.