Psychometric evaluation of the Advanced Systemic Mastocytosis Symptom Assessment Form (AdvSM-SAF)

Leuk Res. 2021 Sep:108:106606. doi: 10.1016/j.leukres.2021.106606. Epub 2021 May 1.

Abstract

Background: The Advanced Systemic Mastocytosis Symptom Assessment Form (AdvSM-SAF) was developed to evaluate symptoms of advanced systemic mastocytosis (AdvSM). This study aimed to psychometrically evaluate AdvSM-SAF scores and provide score interpretation guidelines.

Methods: The 10-item AdvSM-SAF was administered daily (scored as a seven-day average) in EXPLORER, an open-label Phase 1 study in AdvSM. Score distribution, reliability, construct-related validity, sensitivity to change, and interpretation guidelines were evaluated for AdvSM-SAF items, gastrointestinal symptom score (GSS), skin symptom score (SSS), and total symptom score (TSS).

Results: Thirty-one patients contributed to the analyses. At Baseline, the GSS, SSS, and TSS had adequate internal consistency (α > 0.7) and test-retest reliability (intraclass correlation coefficients >0.7). AdvSM-SAF scores were moderately to strongly correlated with variables as expected, and distinguished among clinically distinct groups. Observed relationships between change scores in the AdvSM-SAF and other assessments reflect evidence that AdvSM-SAF scores change in concert with other assessments designed to measure similar constructs. The magnitude of AdvSM-SAF weekly TSS mean change scores based on different anchor groupings was as expected (improvement > stable > worsening). Candidate clinically meaningful between-group difference estimates (GSS = 2-4, SSS = 2-3, and TSS = 4-7 points) and within-person change estimates (GSS = 6-9, SSS = 1-4, TSS = 9-14) for AdvSM-SAF weekly scores were generated.

Conclusion: The AdvSM-SAF produced reliable, construct-valid, and sensitive scores when administered in the target patient population. These results, along with its strong development history and evidence of content validity, indicate that the AdvSM-SAF is fit for the purpose of measuring treatment benefit in individuals with AdvSM.

Keywords: Advanced systemic mastocytosis; Instrument development; Patient-reported outcomes; Psychometric evaluation.

Publication types

  • Clinical Trial, Phase I
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Mastocytosis, Systemic / diagnosis*
  • Mastocytosis, Systemic / epidemiology
  • Mastocytosis, Systemic / psychology*
  • Middle Aged
  • Prognosis
  • Psychometrics / methods*
  • Quality of Life*
  • Reproducibility of Results
  • Severity of Illness Index*
  • Surveys and Questionnaires
  • Symptom Assessment / methods*
  • United Kingdom / epidemiology
  • United States / epidemiology