The Mastocytosis Control Test: A Patient-Reported Outcome Measure Assessing Disease Control

Background: Mastocytosis is characterized by expanding neoplastic mast cells in organs such as the skin, bone marrow, and gastrointestinal tract. The release of mast cell mediators triggers cutaneous, gastrointestinal, and other symptoms. Currently, no validated mastocytosis-specific patient-reported outcome measure (PROM) exists to assess disease control.

Objective: Here, we developed a disease-specific instrument, the Mastocytosis Control Test (MCT), for evaluating and monitoring disease control in patients with nonadvanced disease.

Methods: Six potential MCT items were generated using a combined approach consisting of a literature review, patient interviews, and expert input. Item selection and reduction were performed by impact analysis and interitem correlation, followed by expert reviews and cognitive debriefings. In a validation study, the resulting MCT was tested for validity and reliability by assessing internal consistency, test-retest reliability, convergent validity, known-groups validity, and receiver operating characteristics (ROC) analysis.

Results: Ten patients participated in the item generation phase and 101 in the item reduction and validation phase. The final MCT consisted of 5 items. Our methods showed a valid total score, high internal consistency, and test-retest reliability. Convergent and known-groups validity demonstrated a strong correlation with related anchors. The ROC curve analysis suggested a cutoff value of ≥13 points to identify patients with good disease control.

Conclusions: The MCT is a disease-specific, valid, and reliable PROM for adult patients with nonadvanced disease. It may measure and monitor disease control in routine daily practice and clinical trials.