Validation and Clinical Meaningfulness of the 18-item National Comprehensive Cancer Network-Functional Assessment of Cancer Therapy (NCCN-FACT) Lymphoma Symptom Index (NFLymSI-18) in Patients with Lymphoma.

[OBJECTIVES] To further evaluate the psychometric properties of the National Comprehensive Cancer Network-Functional Assessment of Cancer Therapy (NCCN-FACT) Lymphoma Symptom Index-18 (NFLymSI-18), including estimates of meaningful within-patient change thresholds, to support its ability to reliably and validly measure clinical- and patient-relevant outcomes in diverse research settings.

[METHODS] Data from a longitudinal multicenter clinical trial in patients with indolent B-cell lymphoma and a single-institution observational study of patients with Hodgkin's and non-Hodgkin's lymphoma were examined using inferential statistics. Available data were analyzed separately and then used collectively to summarize evidence of NFLymSI-18 reliability and validity. Effect sizes for known-groups comparisons and responsiveness analyses were calculated to determine meaningful score thresholds.

[RESULTS] Analyses indicated that the NFLymSI-18 demonstrated good internal consistency reliability (Cronbach's alpha >0.70) for all three subscales (with two >0.80), and excellent (>0.90) for the NFLymSI-18 Total in the observational study. Stability (test-retest reliability) exceeded preset thresholds for good reliability for total score and all but one subscale. Known-groups analysis confirmed construct validity, often with moderate-to-large effect sizes, particularly between categories of performance status ratings in the observational study (effect size between -0.33 to -1.06). Responsiveness to changes in clinical status was significant, indicating a sensitivity to within-patient clinical changes. Clinically meaningful individual patient change thresholds were estimated to be 5-6 points for the NFLymSI-18 Total score and 2-4 points for the Disease-Related Symptoms - Physical (DRS-P) score.

[CONCLUSION] The NFLymSI-18 is reliable, valid, and responsive, and includes suggested values for individual patient change when planning lymphoma clinical trials.