Table 2.
Internal consistency reliability and construct (convergent/divergent, clinical) validity of the FACT-M in the MCC population (n = 172)
| FACT-M subscale, summary and MCC-specific scores | # items | Cronbach’s alpha[a] | McDonald’s coefficient omega | Scale structure | ECOG PS (mean [SD]) | |||
|---|---|---|---|---|---|---|---|---|
| Range of item-subscale correlations[b] | Convergent[c]/ divergent[d] validity (% of items) | 0 (n = 106) | 1 (N = 66) | p-value[e] | ||||
| FACT-G subscales | ||||||||
| Physical well-being | 7 | 0.84 | 0.85 | 0.53–0.71 | 100 / 57 | 24.0 (4.2) | 21.3 (5.6) | <.001 |
| Social/Family well-being[f] | 6 | 0.83 | 0.85 | 0.55–0.70 | 100 / 100 | 22.5 (5.4) | 21.6 (5.7) | 0.308 |
| Emotional well-being | 6 | 0.80 | 0.80 | 0.36–0.70 | 83 / 67 | 18.1 (4.1) | 16.8 (5.0) | 0.0499 |
| Functional well-being | 7 | 0.89 | 0.89 | 0.52–0.77 | 100 / 71 | 18.1 (6.7) | 15.8 (6.4) | 0.028 |
| Melanoma-specific subscales | ||||||||
| Melanoma subscale | 16 | 0.84 | 0.86 | 0.19–0.76 | 50 / 38 | 54.3 (7.5) | 50.6 (9.0) | 0.004 |
| Melanoma surgery scale | 8 | 0.82 | 0.83 | 0.20–0.77 | 75 / 75 | 27.0 (5.3) | 24.4 (7.1) | 0.007 |
| Summary scales | ||||||||
| FACT-M TOI | 30 | 0.94 | – | – | – | 96.4 (16.7) | 88.1 (19.5) | 0.003 |
| FACT-G Total score | 27 | 0.93 | – | – | – | 82.8 (16.2) | 75.5 (18.1) | 0.007 |
| FACT-M Total score | 43 | 0.95 | – | – | – | 137.0 (22.3) | 126.6 (25.8) | 0.006 |
| MCC-Specific scores | ||||||||
| Physical function score (PF) | 6 | 0.89 | 0.89 | 0.61–0.76 | 100 / 100 | 17.2 (5.5) | 14.3 (5.9) | 0.001 |
| Psychological impact score (PI) | 6 | 0.84 | 0.85 | 0.55–0.72 | 100 / 100 | 18.4 (4.3) | 17.0 (5.2) | 0.064 |
| MCC summary score | 12 | 0.90 | – | – | – | 35.5 (8.7) | 31.3 (10.0) | 0.004 |
# = number; ECOG PS = Eastern Cooperative Oncology Group performance score (0 = fully active; 1 = restricted in physically strenuous activity); MCC = Merkel cell carcinoma; SD = Standard deviation, TOI = Trial Outcome Index
[a] Recommended threshold α > 0.7; [b] Pearson correlation coefficients; [c] % of items correlated with its own dimension ≥0.4; [d] % of items correlated with its own dimension higher that the correlation with any other dimension; [e] p-value from t-test of score between the two ECOG performance status groups at baseline; [f] convergent and divergent validity were calculated without the ‘satisfaction with sex life’ item due to high item missingness resulting from response to this item being voluntary