Iterative qualitative approach to establishing content validation of a patient-reported outcome measure for arm lymphedema: the LYMPH-Q Upper Extremity Module.

Background: Breast cancer-related lymphedema (BRCL) is one of the most common causes of upper extremity (UE) lymphedema in developed nations and substantially impacts health-related quality of life. To advance our understanding of the epidemiology and treatment of BRCL, rigorously developed and validated patient-reported outcome measures (PROMs) are needed. This study aimed to demonstrate the iterative content validity of a modular UE lymphedema-specific PROM called the LYMPH-Q UE module.

Methods: A multi-step iterative qualitative approach was used. Semi-structured interview data from in-depth qualitative interviews with adult women (18 years and older) with BCRL were used to develop the first set of the LYMPH-Q UE scales. The content validity of these scales was demonstrated with patient and clinician feedback. Over the course of cognitive debriefing interviews, additional concepts of lymphedema worry and impact on work were identified as missing from the LYMPH-Q UE module. Subsequently, two new qualitative studies (a focus group and in-depth concept elicitation interviews with patients) were conducted, and two new scales were developed to measure lymphedema worry and impact on work life and their content validity was demonstrated.

Results: Qualitative data from in-depth and cognitive interviews with 15 (age 40-74 years) and 16 (age 38-74 years) women with BRCL, respectively, and feedback from 12 clinical experts, were used to develop and demonstrate the content validity of six LYMPH-Q UE scales measuring symptoms, function, appearance, psychological, information, and arm sleeve. Additionally, data from in-depth interviews with 12 (age 35-72 years) women with UE lymphedema and four focus groups (n = 16 women; age 35-74 years) was used to develop and assess the content validity of two new LYMPH-Q UE scales measuring lymphedema worry and impact on work life. The content validity of the previously established six scales was also demonstrated in these subsequent qualitative studies.

Conclusion: The LYMPH-Q UE is a modular PROM developed using international guidelines for PROM development and can be used in clinical practice, research, and quality improvement to enhance patient-centered shared decision-making. This study's innovative and iterative approach to content validation demonstrates that the LYMPH-Q UE is a comprehensive measure that includes important concepts relevant to patients with UE lymphedema.