Minimally important differences in the Mahler's Transition Dyspnoea Index in a large randomized controlled trial--results from the Scleroderma Lung Study.
OBJECTIVE
Scleroderma Lung Study (SLS) showed that cyclophosphamide (CYC) was better than placebo (PLA) in preventing progression of forced vital capacity percentage (FVC%) predicted and dyspnoea at 12 months. Our objective was to assess minimally important difference (MID) for Mahler's Transition Dyspnoea Index (TDI) in SLS.


METHODS
A total of 158 subjects participated in the SLS. Data from the two treatment groups were combined for this analysis. We used five patient-reported anchors from the short form (SF)-36 instrument to assess MID for TDI-SF-36 transition question and four questions from SF-36 pertaining to walking on a flat surface or climbing stairs. On the SF-36 transition question, patients who rated as a little better or a little worse were defined as the MID subgroup. For other questions, patients who reported improvement from 'Limited a lot' to 'Limited a little' and 'Limited a little' to 'No limit' and vice versa were defined as the MID subgroup.


RESULTS
The MID estimates for the TDI improvement and worsening ranged from 1.05 to 2.16 (mean score = 1.5) U and from -0.61 to -2.55 (mean score = -1.5) U, respectively. Change in this group was larger than that of the no-change group (mean score = 0.38 U). Patients who achieved the MID for improvement at 12 months had a greater improvement in their FVC% predicted (3.6%) compared with those who did not (-3.3%; P < 0.001).


CONCLUSIONS
A change (improvement/worsening) of 1.5 U in the TDI is the MID for SSc-related interstitial lung disease (SSc-ILD). This can aid in interpreting clinically important changes in breathlessness in SSc-ILD.
Khanna
Dinesh
D
Department of Medicine, Division of Rheumatology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA. dkhanna@mednet.ucla.edu
Tseng
Chi-Hong
CH
Furst
Daniel E
DE
Clements
Philip J
PJ
Elashoff
Robert
R
Roth
Michael
M
Elashoff
David
D
Tashkin
Donald P
DP
D000328:Adult; D003520:Cyclophosphamide / Q000627:therapeutic use; D004311:Double-Blind Method; D004417:Dyspnea / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D017563:Lung Diseases, Interstitial / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012595:Scleroderma, Systemic / Q000150:complications* / Q000188:drug therapy / Q000503:physiopathology; D012720:Severity of Illness Index; D016896:Treatment Outcome; D014797:Vital Capacity
D007166:Immunosuppressive Agents; D003520:Cyclophosphamide