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

From: 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

FACT-M subscale and summary scores0.2*SDBL0.5*SDBLSEM[a]Anchor[b]Range (min-max)[c]Range rounded (min-max)[d]Published MIDs for FACT-M[e]
FACT-G subscales
 Physical well-being0.992.471.950.460.46–2.471–32–3 †
 Social/Family well-being1.092.742.260.720.72–2.741–3 
 Emotional well-being0.902.242.022.370.90–2.371–32†
 Functional well-being1.333.332.250.340.34–3.331–42–3†
Melanoma-specific subscales
 Melanoma subscale1.654.133.311.741.65–4.132–52–4 ¥
  Melanoma surgery scale1.233.082.630.690.69–3.081–31–2 ¥
Summary scales
 FACT-M Trial Outcome Index (TOI)3.408.504.302.542.54–8.503–95–9 ¥
 FACT-G Total score3.448.604.593.903.44–8.604–95–7 †
 FACT-M Total score4.8312.085.615.644.83–12.085–12 
MCC-Specific scores
 FACT-M Physical function score1.152.881.93−0.091.15–2.882–3 
 FACT-M Psychological impact score0.942.351.902.940.94–2.941–3 
 FACT-M MCC summary score1.884.712.952.861.88–4.712–5 
  1. [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]