Minimally important differences in the Mahler's Transition Dyspnoea Index in a large randomized controlled trial--results from the Scleroderma Lung Study

Rheumatology (Oxford). 2009 Dec;48(12):1537-40. doi: 10.1093/rheumatology/kep284. Epub 2009 Sep 23.


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).

Conclusion: 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cyclophosphamide / therapeutic use
  • Double-Blind Method
  • Dyspnea / diagnosis*
  • Dyspnea / etiology
  • Dyspnea / physiopathology
  • Female
  • Humans
  • Immunosuppressive Agents / therapeutic use
  • Lung Diseases, Interstitial / diagnosis*
  • Lung Diseases, Interstitial / etiology
  • Lung Diseases, Interstitial / physiopathology
  • Male
  • Middle Aged
  • Quality of Life
  • Scleroderma, Systemic / complications*
  • Scleroderma, Systemic / drug therapy
  • Scleroderma, Systemic / physiopathology
  • Severity of Illness Index*
  • Treatment Outcome
  • Vital Capacity


  • Immunosuppressive Agents
  • Cyclophosphamide