Abstract
BackgroundIndolent systemic mastocytosis (ISM) is a rare, clonal mast cell neoplasm characterized by severe, unpredictable symptoms. The Indolent Systemic Mastocytosis Symptom Assessment Form (ISM-SAF) items compose a Total Symptom Score (TSS), Gastrointestinal Symptom Score (GSS), and Skin Symptom Score (SSS) to assess symptom severity. This study evaluated the psychometric performance of ISM-SAF among ISM patients.MethodsIn PIONEER, a Phase 2 trial evaluating safety and efficacy of selective kinase inhibitor avapritinib in patients with ISM, the 12-item ISM-SAF was administered daily. Psychometric evaluation of score reliability, validity, and clinical interpretation was conducted using the trial data.ResultsThirty-eight patients contributed to analyses (78.9% female; mean age = 49). Baseline internal consistency reliability (α) for bi-weekly TSS, GSS, and SSS was 0.86, 0.83, and 0.82, respectively. Test–retest reliability among patients exhibiting no change in Patient Global Impression of Symptom Severity (PGIS) between Baseline and Day 15 exceeded 0.74 universally. Construct validity and known-groups analysis showed moderate to strong ISM-SAF score correlation (r = 0.382–0.881) to supportive patient-reported questionnaires (e.g., PGIS and Mastocytosis Quality of Life Questionnaire) symptom and skin scores, and ability to distinguish among clinically unique groups. Correlations of ISM-SAF and other assessment change scores reflect evidence of score sensitivity. Clinically important difference and response estimates were 7–10 and 19, respectively.DiscussionISM-SAF produced reliable, construct-valid, sensitive scores when administered in PIONEER to patients in the target population. Results of this study support the use of the ISM-SAF as a reliable and valid measure to evaluate disease symptomology in ISM patients.Trial registration ClinicalTrials.gov, NCT03731260. Registered 10 October 2018, https://clinicaltrials.gov/ct2/show/study/NCT03731260.
Highlights
Systemic mastocytosis is a rare, clonal mast cell neoplasm driven by the KIT D816V mutation [1], characterized by uncontrolled proliferation and activation of mast cells that leads to severe and unpredictable symptoms for patients with systemic mastocytosis [2]
Score distribution Descriptive analysis of the Indolent systemic mastocytosis (ISM)-SAF indicated that, while patients used the range of response options available to them for each item (i.e., 0 to 10), not all patients reported experiencing all symptoms and, when symptoms were reported, severity rates were variable
As a wider range of values were available for the Indolent Systemic Mastocytosis Symptom Assessment Form (ISM-SAF) at C3D1 and C4D1, the correlations among items were generally enhanced at the later timepoints
Summary
Systemic mastocytosis is a rare, clonal mast cell neoplasm driven by the KIT D816V mutation [1], characterized by uncontrolled proliferation and activation of mast cells that leads to severe and unpredictable symptoms for patients with systemic mastocytosis [2]. Measurement-focused analyses were executed based on blinded data from Part 1 of the Phase 2 PIONEER trial to evaluate the performance of scores produced by the ISM-SAF with respect to score variability, distribution, and missingness; reliability; constructrelated validity; and sensitivity to change. Indolent systemic mastocytosis (ISM) is a rare, clonal mast cell neoplasm characterized by severe, unpredictable symptoms. The Indolent Systemic Mastocytosis Symptom Assessment Form (ISM-SAF) items compose a Total Symptom Score (TSS), Gastrointestinal Symptom Score (GSS), and Skin Symptom Score (SSS) to assess symp‐ tom severity. This study evaluated the psychometric performance of ISM-SAF among ISM patients
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