Background: Pemphigus Disease Area Index (PDAI) and Autoimmune Bullous Skin Disorder Intensity Score (ABSIS) are the most extensively validated severity outcome measures for pemphigus. However, responsiveness and Minimal Clinically Important Difference (MCID) have not been established. Previous studies determining severity cut-offs have yielded inconsistent results. 
Objectives: To ascertain the responsiveness of the PDAI and ABSIS, establish MCID and re- affirm cut-offs.
Methods: Prospective and retrospective cohort data collected from 2014-2016 from 28 patients with pemphigus at each routine visit. Patients were evaluated using the PDAI, ABSIS, Physician Global Assessment Visual Analog Scale (PGA-VAS), Physicians Subjective Assessment of Disease Severity (PSADS), and Likert scale of the magnitude of change. The Likert scale and PGA-VAS were used for responsiveness by using Pearson’s correlation coefficient. MCID was obtained by setting a responder score of ≥|2| on the PGA- VAS, and ≥|3| on the Likert scale. Cut-scores were reaffirmed using PSADS. 
Results: For responsiveness, using the Likert scale r=-0.4752 (p<0.001), r=0.0869 (p=0.458), r= -0.4574 (p<0.001) for PDAI activity, damage, and ABSIS, respectively. Using the PGA, r=0.4634(p=002), r=-0.1361 (p=0.390), r=0.2559 (p=0.106) for PDAI activity, damage, and ABSIS, respectively. MCID for the PDAI was +/-3 and +/-8.5 for the ABSIS. Disease severity cut-offs of 1/5/38 for the PDAI and 0.3/3.3/20 for the ABSIS were suggested to distinguish none, mild, moderate and severe disease 
Limitations: A limited number of patients, patients with limited disease extent. Conclusion: The PDAI is more responsive than the ABSIS. PDAI damage is not responsive. Standardised and practical use of the PDAI is now possible.

Responsiveness,  Minimal Clinically Important Difference (MCID),  and cut-offs for the Pemphigus Disease Area Index (PDAI) and Autoimmune Bullous Skin disorder Intensity Score (ABSIS) for Pemphigus