International validation of the Bullous Pemphigoid Disease Area Index severity score and calculation of cut‐off values for defining mild, moderate and severe types of bullous pemphigoid*

Abstract

Summary Background The Bullous Pemphigoid Disease Area Index (BPDAI) score has been proposed to provide an objective measure of bullous pemphigoid (BP) activity. Objectives The objective of this study was to calculate BPDAI cut‐off values defining mild, moderate and severe BP. We also aimed to assess the interrater reliability and correlation with the number of daily new blisters, and anti‐BP180 and anti‐BP230 antibodies. Methods Severity scores were recorded by two blinded investigators. Anti‐BP180 and anti‐BP230 antibodies were measured using an enzyme‐linked immunosorbent assay (ELISA). Cut‐off values defining mild, moderate and severe subgroups were calculated based on the 25th and 75th percentiles of the BPDAI score. Results In total, 285 patients with BP were enrolled from 50 dermatology departments in Europe. Median BPDAI activity was 37·5 points (range 0–164). Cut‐off values corresponding to the first and third quartiles of the BPDAI score were 20 and 57, respectively; thus, these values were used to define mild (≤ 19), moderate (≥ 20 and ≤ 56) and severe (≥ 57) BP. The median BPDAI score for patients with ≤ 10 daily new blisters was 26 [interquartile range (IQR) 17–45], and for patients with > 10 daily new blisters the median score was 55 (IQR 39–82). The BPDAI intraclass correlation coefficient measured at baseline was 0·97 and remained higher than 0·90 up to month 6. The improvement in the BPDAI score was correlated with the absolute decrease in anti‐BP180 ELISA value (Spearman’s rank r = 0·34, P < 0·004), but not with anti‐BP230 antibodies (r = 0·17, P = 0·15). Conclusions This study suggests cut‐off values of 20–57 for BPDAI to distinguish mild, moderate and severe BP, and confirms that it is a robust tool to assess BP severity precisely.

Classifying the severity of bullous pemphigoid disease

“…An alternative way of measuring disease severity in BPD that also accounts for aspects like urticarial and erythematous reactions is discussed: the BPD Area Index (BPDAI) 3 . In this issue of the BJD , Masmoudi et al 4 . confirm previous results indicating high interrater reliability of this measure 5 .…”

“…To conclude, the study by Masmoudi et al 4 . supports the BPDAI as both reliable and valid.…”

“…Interrater reliability is a prerequisite for use of the BPDAI as a measure of improvement in clinical practice, even when assessed by different clinicians at different points in time. Masmoudi et al 4 . also report convergent validity of the BPDAI by demonstrating its correlation with BP180 antibodies and blood eosinophil count.…”

“…In addition, Masmoudi et al 4 . propose cut‐off scores for the severity classification of patients according to their BPDAI results, based on empirical distribution of the scores in their clinical sample.…”

The association of bullous pemphigoid with dipeptidyl-peptidase 4 inhibitors: a ten-year prospective observational study

“…For multivariate analysis variables with p < 0.1 at univariate analysis or with clinical significance were used. A value of Bullous Pemphigoid Disease Area Index (BPDAI) greater than 56 was used as a measure of severe BP as previously published [4] (This cut off value was identical with the median value of BPDAI in our study cohort).…”