Development of a Cold Agglutinin Disease-Specific Patient-Reported Outcome Symptom Measure

Introduction

Cold agglutinin disease (CAD) is a rare autoimmune hemolytic anemia in which red blood cells are bound by cold agglutinin autoantibodies. In addition to cold-induced symptoms, patients with CAD experience symptoms of chronic anemia and hemolysis including fatigue, weakness, and shortness of breath (Swiecicki PL et al. Blood 2013;122(7):1114-21). The objectives of this study were to identify disease-related symptoms and impacts most important to patients with CAD, and to evaluate whether existing patient-reported outcome (PRO) measures are appropriate to assess relevant CAD concepts.

Methods

As part of a larger study, qualitative concept elicitation (CE) interviews were conducted to better understand the disease burden of CAD from the patient perspective. The results from the first set of interviews were reported by Su J et al. Blood 2020;136(1):29-30. Based on the identified symptoms and impacts, standard survey methodological principles were used to develop a draft item pool to address concepts of interest. Items were refined and evaluated during the second set of interviews, which included 3 rounds of 60-minute phone interviews with patients with CAD using a semi-structured interview guide that included a CE section and cognitive debriefing. Pooled results from both sets of interviews were used to develop a conceptual model of the symptoms and impacts of CAD. Physician advisors were also invited to review the concepts identified in the interviews and to select those that they believed were most relevant as part of an advisory board.

A PubMed review of literature published between 2010-2020 was also conducted to identify existing PRO measures used in the assessment of symptoms, impacts, and/or quality of life and patient experiences in adults with CAD or similar disease areas. Identified PRO measures were assessed to determine the extent to which they captured CAD-specific concepts identified in the CE interviews.

Results

In total, 37 participants diagnosed with primary or secondary CAD took part in the interviews (Set 1, n=16; Set 2, n=21). Overall, the mean age of participants was 67.2 years (range: 35-87), and the majority were female (73%).

The most frequently reported symptom of CAD was reactions to cold environments (n=36; 97%), e.g., cold or numb feet/hands, and skin discoloration. Other reported symptoms included fatigue (n=35; 95%), shortness of breath (n=28; 76%), and trouble with thinking/concentration (n=21; 57%). The most frequently reported unfavorable impact of CAD was on day-to-day activities (n=32; 87%). Other negative impacts included effects on enjoyable activities (n=29; 78%) e.g., gardening, physical health/activities (n=28; 76%), social/leisure life (n=26; 70%); and mood/emotions (n=24; 65%). Most participants (n=30; 81%) reported they had made lifestyle/behavioral changes to help limit their CAD symptoms, such as wearing extra clothing in places that were likely to be cold. A conceptual model of the symptoms and impacts of CAD was developed based on these data (Figure 1). Physician advisors (n=7) agreed that the patient-reported symptoms and impacts identified during the interviews were relevant concepts to CAD.

Following a literature review, no existing PRO measure was found to adequately address concepts deemed critical to CAD from the patient perspective. Owing to the lack of an existing fit-for-purpose measure, 14 concepts were identified from the interviews to develop an initial draft item pool. During the cognitive debriefing in the second set of interviews, participants (n=21: Round 1 n=8; Round 2 n=7; Round 3 n=6) evaluated these concepts. After 3 rounds of interviews, the new item set yielded 11 items relating to: fatigue; cold sensitivity; dyspnea; wearing extra clothing; limited physical, social, and enjoyable activities; difficulty with usual activities; mood; frustration; and anxiety/stress. Participants reported these items were comprehensive of their experiences with CAD, easy to understand, and would be relevant to gaining a better understanding of individuals' experiences with CAD.

Conclusion

These results support the need for a novel PRO measure(s) that adequately addresses concepts critical to the measurement of CAD symptoms and impacts from the patient perspective.

Figure 1

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Figure 1

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