Update on the psychometric properties and minimal important difference (MID) thresholds of the FACT-M questionnaire for use in treatment-naïve and previously treated patients with metastatic Merkel cell carcinoma

Table 5 Minimum and maximum MID thresholds derived from anchor- and distribution-based methods for FACT-M in MCC

FACT-M subscale and summary scores	0.2*SD_BL	0.5*SD_BL	SEM^[a]	Anchor^[b]	Range (min-max)^[c]	Range rounded (min-max)^[d]	Published MIDs for FACT-M^[e]
FACT-G subscales
Physical well-being	0.99	2.47	1.95	0.46	0.46–2.47	1–3	2–3 †
Social/Family well-being	1.09	2.74	2.26	0.72	0.72–2.74	1–3
Emotional well-being	0.90	2.24	2.02	2.37	0.90–2.37	1–3	2†
Functional well-being	1.33	3.33	2.25	0.34	0.34–3.33	1–4	2–3†
Melanoma-specific subscales
Melanoma subscale	1.65	4.13	3.31	1.74	1.65–4.13	2–5	2–4 ¥
Melanoma surgery scale	1.23	3.08	2.63	0.69	0.69–3.08	1–3	1–2 ¥
Summary scales
FACT-M Trial Outcome Index (TOI)	3.40	8.50	4.30	2.54	2.54–8.50	3–9	5–9 ¥
FACT-G Total score	3.44	8.60	4.59	3.90	3.44–8.60	4–9	5–7 †
FACT-M Total score	4.83	12.08	5.61	5.64	4.83–12.08	5–12
MCC-Specific scores
FACT-M Physical function score	1.15	2.88	1.93	−0.09	1.15–2.88	2–3
FACT-M Psychological impact score	0.94	2.35	1.90	2.94	0.94–2.94	1–3
FACT-M MCC summary score	1.88	4.71	2.95	2.86	1.88–4.71	2–5

[a] SEM is calculated using Cronbach’s alpha based on baseline scores; [b] The anchor used is the EQ VAS score with threshold MID = 7; [c] The range was derived from the minimum and maximum resulting from the various methods, with the exception of the MCC-specific scores where the smallest positive value was used as the negative value was implausible given that the thresholds are proposed to be used for both improvement and worsening; [d] While rounding was generally to the next higher integer, we rounded down in case the first decimal point was a zero; [e] FACT-M MIDs for melanoma published by: †Cella et al. (2002) [1]; ¥ Askew et al. (2009) [2]

ISSN: 1477-7525