We have previously reported on the validation of the 18 item Myeloproliferative Neoplasm Assessment Form (MPN-SAF) (Blood 2011;118:401–408) given in conjunction with the 9 item Brief Fatigue Inventory (BFI) (Cancer 1999;85:1186–1196) to assess symptomatic burden in an international sample of MPN patients (pts), including validation in English, Italian, Swedish, German, French, Spanish, and Dutch. We desired to assess the utility of an average total symptom score (TSS) from the most pertinent and representative MPN symptoms for purposes of assessing the burden of symptoms in MPN pts, and subsequent tracking in response to therapy.
Data was collected among an international cohort of MPN pts and their physicians, including patient demographics and disease features and completion the BFI, MPN-SAF and the EORTC-QLQ-C30. Among pts who completed at least 5 of 10 specific items on the BFI and MPN-SAF, an average score was calculated as the TSS. TSS items included “worst” fatigue from the BFI and 9 items from the MPN-SAF including concentration, early satiety, inactivity, night sweats, itching, bone pain, abdominal discomfort, weight loss and fever. The TSS thus had a possible range of 0–10 with 10 representing the highest level of symptom severity. Data was then analyzed for internal consistency, and divergent, convergent validity, and construct validity.
Patient Demographic and Disease Characteristics:1433 MPN pts were prospectively enrolled (Argentina 22, France 482, Germany 59, Italy 186, Netherlands 236, Puerto Rico 10, United Kingdom 57, United States 102, Spain 157, Sweden 114, Uruguay 8) including 594 ET, 538 PV and 293 MF pts (8 missing; MF: 61% Primary MF, 23% post-ET MF, 15% post-PV MF). 1408 pts completed at least 5 of the 10 items necessary to calculate a TSS. Pts were of characteristic age (mean 62, range 20–94) and gender (54% female) common to disease. TSS Burden of MPN Symptoms: Consistent with prior studies, the majority of pts (>50%) were symptomatic in each TSS item except for items associated with high disease severity, namely bone pain (48.6%), weight loss (30.6%) and fever (18.4%). Fatigue carried the highest symptom intensity (4.4, SD=2.8), followed by problems with concentration (2.5, SD=2.8) and early satiety (2.5, SD=2.7). Overall mean TSS was 2.1 (SD=1.6). Divergent Validity: TSS significantly differed among MPN disease subtypes (p<0.001) with means of 1.9 (SD=1.5), 2.2 (SD=1.6), and 2.5 (SD=1.7) for ET, PV, and MF pts, respectively. Statistically significant differences in TSS were also observed between pts with clinically deficient (>4, n=480) versus non-clinically deficient QOL (<4, n=894; mean 3.3 versus 1.5; p<0.001). When comparing to MD perceptions, TSS was significantly higher when MDs rated >2 of 6 common MPN-related symptoms as clinically significant (2.8, n=400) versus <2 symptoms (1.6, n=726; p<0.001). No significant trends were observed when comparing disease type by the presence of a current medical therapy. Convergent Validity: The TSS was strongly correlated with patient-reported QOL (r=0.59, p<0.001). Overall excellent correlations existed between the TSS and EORTC-QLQ-C30 functional subscales (all p<0.001 and r>0.50 except social functioning [r=0.48]). Additionally, excellent correlations were observed between the TSS and EORTC-QLQ-C30 fatigue and pain symptom scales (r>0.5, p<0.001). Internal Consistency and Construct Validity: The TSS had excellent internal consistency (Cronbach's alpha=0.83). Factor analysis identified a single underlying construct among the 10 TSS items (significant eigenvalues being >1). Factor loadings ranged from 0.43 for fever and weight loss to 0.71 for inactivity. The single factor suggests that the arithmetic mean of the 10 items is an appropriate global TSS score.
The TSS demonstrated excellent psychometric properties. Overall, results of validity and internal consistency indicate that the TSS is a concise, valid, and accurate assessment of symptom burden among MPN pts. This new scoring will facilitate ease of implementation of the MPN-SAF into larger clinical trials and reduce ambiguity associated with interpreting response outcomes. Future analyses to investigate the impact of therapies on TSS are ongoing.
No relevant conflicts of interest to declare.
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