Measurement of Quality of Life in Patients with Mycosis Fungoides/Sézary Syndrome Cutaneous T-Cell Lymphoma: Development of an Electronic Instrument.

Abstract

BackgroundAlthough the quality of life (QoL) plays an important role in treatment decision making and clinical management of mycosis fungoides (MF) or Sézary syndrome (SS) subtypes of cutaneous T-cell lymphomas (MF/SS-CTCLs), an MF- or SS-specific measure of QoL does not exist.ObjectiveThe objective of this research was to develop and validate the first QoL instrument for MF/SS-CTCL using a patient-centered approach.MethodsA conceptual framework for the MF/SS-CTCL QoL was developed through a literature review and interviews with key opinion leaders. Concept elicitation with patients was utilized to refine the conceptual model and generate preliminary items. The items were then revised based on qualitative and quantitative feedback obtained through cognitive debriefing surveys and interviews with patients. Next, participants (N=126) completed the preliminary MF/SS-CTCL QoL and a comparator measure of health-related QoL (Skindex-29) through the PatientsLikeMe Open Research Exchange. The MF/SS-CTCL QoL was completed again 5 days later by 66 participants for the purposes of evaluating test-retest reliability. The MF/SS-CTCL QoL was finalized based on results from an empirical evaluation, which included both classical and modern test theory approaches. Specifically, this included evaluation of (1) the optimal item response theory measurement model; (2) item fit; (3) unidimensionality; (4) rating scale performance; (5) reliability; (6) test information (precision); (7) person-to-item map; (8) convergent and discriminant validity; and (9) presence of bias via differential item function.ResultsResults from the comprehensive psychometric evaluation utilizing a Rasch-Grouped Rating Scale model yielded a final 12-item instrument. The rating scale functioned as expected, and the instrument exhibited adequate person reliability (.87), good to excellent test-retest reliability (r=.89, P<.001), high levels of measurement precision, and good person-to-item targeting. The correlation between the MF/SS-CTCL QoL and the Skindex-29 (r=.852, P<.001) was significantly greater than the correlation between the MF/SS-CTCL QoL and syndrome stage (r=.260, P<.001), providing support for convergent and discriminant validity. Items did not show significant bias based on gender, age, or race. Rasch scores were converted to scaled scores with qualitative descriptive categories for ease of interpretation.ConclusionsEmpirical evaluation demonstrated strong evidence of excellent psychometric properties. Utilizing a patient-centered measure development approach ensures that this QoL instrument captures the information that is most meaningful and clinically relevant to patients.