Poster Presentation 2014 Cutaneous Biology Meeting

The Validity, Reliability and Responsiveness of the Bullous Pemphigoid Disease Area Index (BPDAI) (#15)

Asri Wijayanti 1 2 , Cathy Y Zhao 1 2 , David Boettiger 2 3 , Norito Ishii 4 , Takashi Hashimoto 4 , Dedee F Murrell 1 2
  1. Dermatology, St George Hospital, Sydney, NSW, Australia
  2. University of New South Wales, Sydney, NSW, Australia
  3. The Kirby Institute, Sydney, NSW, Australia
  4. Kurume University, Kurume, Fukuoka, Japan

Background: The BPDAI is the only bullous pemphigoid (BP)-specific disease severity scoring system but it is incompletely validated.

Objective: We seek to evaluate the convergent construct validity, inter-rater and intra-rater reliabilities, and responsiveness in discriminating clinically meaningful changes of BPDAI to ascertain its utility in clinical trials.

Methods: Thirty patients with BP are assessed independently by bullous experts at baseline, month 1 and the subsequent 3-monthly clinic visits using the BPDAI, BPDAI pruritus, Autoimmune Bullous Skin Disorder Intensity Score (ABSIS), Physician Global Assessment (PGA) and the physician’s subjective assessment of clinical improvement. The same physician repeats the scoring after 15minutes without the initial completed sheets. The reliability and validity of BPDAI are compared against anti-BP180 levels and ABSIS (partially validated without separation for activity and damage). The Autoimmune Bullous Disease Quality-of-Life (ABQOL) and the Treatment of Autoimmune Bullous Disease Quality-of-Life (TABQOL) questionnaires are used to measure the subjective element of disease severity. Paired correlation analyses are employed to examine the relationship between the interval changes in BPDAI scores with the PGA scores.

Results: Using preliminary data, the intraclass correlation coefficients (ICCs) (95% confidence intervals) for inter-rater reliability are: BPDAI 0.976 (0.961-0.984) and ABSIS 0.941 (0.910-0.961). For intra-rater reliability, the ICCs are: BPDAI 0.996 (0.986-0.999) and ABSIS 0.991 (0.970-0.997). Using Spearman’s rho correlation, the BPDAI is well-correlated at 0.858 (p=0.000) with ABSIS. The BPDAI has a statistically significant and higher correlation with BPDAI pruritus measure (0.338, p=0.009) than ABSIS with BPDAI pruritus measure (0.160, p=0.225). Both the BPDAI and ABSIS are not significantly correlated with the subjective measures ABQOL and TABQOL.

Limitations: A limited number of patients had severe disease activity. An independent study will be required to demonstrate the reliabilities of BPDAI in patients with widespread disease.

Conclusion: The BPDAI demonstrates excellent reliability, validity and correlates with its subjective pruritus measure.